Odorant Binding Characteristics of Three Recombinant Odorant Binding Proteins in Microplitis mediator (Hymenoptera: Braconidae)

Odorant binding proteins (OBPs) are believed to be important for transporting semiochemicals through the aqueous sensillar lymph to the olfactory receptor cells within the insect antennal sensilla. In this study, three new putative OBP genes, MmedOBP8-10, were identified from a Microplitis mediator (Hymenoptera: Braconidae) antennal cDNA library. Quantitative real-time PCR (qRT-PCR) analysis revealed that all three of the OBP genes were expressed mainly in the antennae of adult wasps. The three OBPs were recombinantly expressed in Escherichia coli and purified by Ni ion affinity chromatography. Fluorescence competitive binding assays were performed using N-phenyl-naphthylamine as a fluorescent probe and 45 small organic compounds as competitors. These assays demonstrated that the three M. mediator OBPs can bind a broad range of odorant molecules with different binding affinities. They can bind the following ligands: nonane, farnesol, nerolidol, nonanal, β-ionone, acetic ether, and farnesene. In a Y-tube assay with these ligands as odor stimuli and paraffin oil as a control, all ligands, except nerolidol and acetic ether, were able to elicit behavioral responses in adult M. mediator. The wasps were significantly attracted to β-ionone, nonanal, and farnesene and repelled by nonane and farnesol. The results of this work provide insight into the chemosensory functions of the OBPs in M. mediator.     

Effect ofβ-lonone onaspergillus flavus andaspergillus parasiticus growth,sporulation, morphology and aflatoxin production

The ketoneβ-ionone is reported to be one of the naturally occurring volatile metabolites of developing corn ears. In testing the effects of volatile compounds onAspergillus flavus andA. parasiticus, we found thatβ-ionone applied to the surface of PDA plates had a striking inhibition of growth and sporulation of these fungi. The colonies were restricted, remained buff-colored and had little or no sporulation. There were major effects on the morphology of the asexual reproductive structures. The conidiophore development was arrested and normal sporulation did not occur. Mycelial transfers from these atypical cultures to potato dextrose agar had normal growth and conidia. Incorporation ofβ-ionone at levels of 10-1000μL/L, in liquid media seeded with spore suspensions ofA. parasiticus (NRRL 2999) severely depressed aflatoxin accumulation in shake culture.     

Identification and Molecular Cloning of Putative Odorant-Binding Proteins and Chemosensory Protein from the Bethylid Wasp, <Emphasis Type="Italic">Scleroderma guani</Emphasis> Xiao et Wu

Two putative odorant-binding proteins (OBPs) and one putative chemosensory protein (CSP) from females of the ant-like bethylid wasp, Scleroderma guani Xiao et Wu (Hymenoptera: Bethylidae), were identified and cloned. The putative OBPs and CSP were identified by nondenaturing polyacrylamide gel electrophoresis (native-PAGE). 3′ rapid amplification of cDNA ends (3′RACE) was performed to obtain the sequences of the mature proteins by using degenerate primers designed from N-terminal sequences. Gene-specific primers for 5′ rapid amplification of cDNA ends (5′RACE) were designed according to 3′RACE results and used in polymerase chain reaction (PCR) to obtain full-length sequences. The proteins (Sgua-OBP1, Sgua-OBP2, and Sgua-CSP1) encode 133, 142, and 129 amino acid-deduced sequences, respectively. Prediction of signal peptide sequences matches the N-terminal amino acid sequence of the isolated proteins. Database searches suggest that the Sgua-OBP1 and Sgua-OBP2 are homologs of OBPs from other insects, and Sgua-CSP1 shares a high level of identity with previously described CSPs. Daguang Lu and Xiangrui Li contributed equally to this work     

New Attractants for Males of the Solanaceous Fruit Fly <Emphasis Type="Italic">Bactrocera latifrons</Emphasis>

α-Ionone, α-ionol, and their mixtures with phenolic volatiles act as potential male lures for the solanaceous fruit fly Bactrocera latifrons (Hendel). However, the attractiveness of these compounds is not as strong as that of other well-known tephritid male lures, such as methyl eugenol for Bactrocera dorsalis. Isophorone and isophorol, which have a partial skeletal structure of α-ionone/α-ionol (i.e., trimethylcyclohexene), were attractive to B. latifrons males, and their mixtures with α-ionol exhibited stronger activity than any of the individual compounds. We also tested 3-oxo-α-ionone, 3-oxo-α-ionol, 3-hydroxy-α-ionone, and 3-hydroxy-α-ionol, hybrid compounds between isophorone/isophorol and α-ionone/α-ionol. 3-Oxo-α-ionone and 3-oxo-α-ionol were active both as attractants and phagostimulants for males. The results suggest that the introduction of an oxygen atom at the 3-position of the α-ionone/α-ionol molecule optimizes the specific chemosensory responses in B. latifrons males.     

Two Novel Ceramides with a Phytosphingolipid and a Tertiary Amide Structure from <Emphasis Type="Italic">Zephyranthes candida</Emphasis>

Two novel ceramides, Candidamide A (1) with a phytosphingolipid structure, and Candidamide B (2) with a tertiary amide structure, together with 12 known compounds (3–14) have been isolated from the bulbs of Zephyranthes candida, The structures of 1 and 2 have been elucidated to be 1,3,5,6-tetrahydroxy-2-(2′-hydroxytetracosanoyl amino)-8-(E)-octadecadiene (1) and (2S,3S,4R,8E,2′R)-2-[N-(2′-hydroxyoctadecanoyl)-N-(1′′,2′′-dihydroxyethyl)-amino]-8-hexacosene-1,3,4-triol (2) on the basis of spectroscopic evidence including IR, MS, NMR (¹H-NMR, ¹³C-NMR, DEPT, ¹H–¹H COSY, HSQC, HMBC). The known compounds were identified as (2S)-3′,7-dihydroxy-4′-methoxyflavan (3), (2S)-4′-hydroxy-7-methoxyflavan (4), (2S)-4′,7-dihydroxyflavan (5), 7-hydroxy-3′, 4′-methylenedioxyflavan (6), ambrettolide (7), β-sitostero1 (8), β-daucosterin (9), rutin (10), pancratistatin (11), lycorine (12), haemanthidine (13), and haemanthamine (14). In the antimicrobial assay, candidamide A (1) and candidamide B (2) displayed moderate activities against bacteria Staphylococcus aureus and Escherichia coli, and fungi Aspergillus niger, Candida albicans and Trichophyton rubrum.     

New cerebrosides from the basidiomycete <Emphasis Type="Italic">Cortinarius tenuipes</Emphasis>

Five cerebrosides (1–5), including three new ones named cortenuamide A (1), cortenuamide B (2), and cortenuamide C (3), were isolated from the fruiting bodies of the basid-iomycete Cortinarius tenuipes. The structures of those compounds were elucidated as (4E,8E)-N-d-2′-hydroxytetracosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (1), (4E,8E)-N-d-2′-hydroxytricosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8 sphingadienine (2), (4E, 8E)-N-d-2′-hydroxydocosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (3), (4E, 8E)-N-d-2′-hydroxyoctadecanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (4), and (4E, 8E)-N-d-2′-hydroxypalmitoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (5) by spectral and chemical methods.     

Structural analogy between β′ triacylglycerols and n-alkanes. Toward the crystal structure of β′-2 p.p+2.p triacylglycerols

The structural elements of the β′-2 polymorph of 1,3-dilauroyl-2-myristoylglycerol as found by Birker et al. (J. Am. Oil Chem. Soc. 68:895–906, 1991) were also observed in the crystal structures of other long-chain compounds. This analogy led to the assembly of a β′-2 structure at the atomic level from known crystallographic data. The structure was optimized by molecular mechanics and was consistent with experimental data, including satisfactory reproduction of the X-ray powder pattern. To the best of our knowledge, this is the first β′ structure with a 1,2 configuration and an intramolecular orthorhombic subcell which is fully optimized by molecular mechanics to date. It shows all structural elements found earlier by Birker et al.     

Binary Phase Behavior of 1,3-Dipalmitoyl-2-oleoyl-<Emphasis Type="Italic">sn</Emphasis>-glycerol and 1,2-Dioleoyl-3-palmitoyl-<Emphasis Type="Italic">rac</Emphasis>-glycerol

1,3-Dipalmitoyl-2-oleoyl-sn-glycerol (POP) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP) are two major molecular species that account for roughly half of the total triacylglycerols in palm oil. The binary phase behavior of a POP/OOP mixture plays an important role in the crystallization of palm oil. We conducted thermodynamic and kinetic studies of OOP and its mixtures with POP using differential scanning calorimetry and X-ray diffraction with a conventional generator and synchrotron radiation. We found that OOP has two polymorphs, α as a metastable form and β′ as the most stable form, and that the two forms are stacked in a triple-chain-length structure. The POP/OOP mixtures exhibited immiscible eutectic natures in both their metastable and their most stable states, in contrast to POP/1,2-dipalmitoyl-3-oleoyl-rac-glycerol and POP/1,3-dioleoyl-2-palmitoyl-sn-glycerol mixtures, in which molecular compounds of a double-chain-length structure were formed. A time-resolved synchrotron radiation X-ray diffraction study undertaken during the cooling and heating processes indicated that the α and β′ forms of the POP and OOP fractions crystallized and melted in separate manners, and that crystallization of the β′ form and the polymorphic transformation from α to β′ of POP and OOP are promoted in the presence of another component. The absence of molecular compound crystals in the binary mixtures of POP/OOP is explained by taking into account the molecular interactions of acyl chain packing, glycerol conformation, and methyl end stacking, among which glycerol conformation appeared to be most influential.     

Polymorphic transformations in sn-1, 3-distearoyl-2-ricinoleyl-glycerol

Polymorphic transformations of sn-1,3-distearoyl-2-ricinoleyl-glycerol (SRS) have been studied with differential scanning calorimetry, X-ray powder diffraction (XRD), synchrotron radiation X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR) techniques by using a 99.8% pure sample. Four polymorphs, α, γ, β′₂, and β′₁, were isolated. The thermal behavior of the four forms showed that the fusion of α at 25.8°C was followed by the crystallization of γ which melts at 40.6°C, and β′₂ and β′₁ revealed melting peaks at 44.3 and 48.0°C, respectively. No β form was observed, even when the two β′ forms were annealed around their melting points over one week. The XRD long spacing indicates that α packs into a double chain-length structure; however, γ and the two β′ phases pack into a triple chain-length structure. The polarized and nonpolarized FTIR spectra in methylene scissoring and methylene rocking regions indicated a parallel subcell packing in γ, and a mixture of orthorhombic perpendicular and parallel or hexagonal subcells in the β′₂ and β′₁ phases. Consequently, SRS exhibits quite a unique polymorphic behavior, compared to tristearoyl glycerol and sn-1,3-distearoyl-2-oleoyl-glycerol.     

Kinetics of melt crystallization and transformation of tripalmitin polymorphs

The rates of melt crystallization and phase transformation of three polymorphs of tripalmitin were examined by optical microscopy, X-ray diffractometry and DSC with and without surfactant additives (sorbitan mono- and tristearates). The following results were obtained: (a) Crystallization rate increased in order ofα, β′ andβ; (b) transformation rate was slower than crystallization rate for each polymorph at the same temperature examined; (c) when the most stableβ form was recrystallized from the melt just after the melting ofα, its recrystallization rate was much higher than that by simple melt-cooling; (d) surfactant additives retarded both the crystallization and transformation of all the polymorphs, yetβ′ was influenced the most. A mechanistic interpretation based on the molecular structures both of the melt and of each polymorph is presented.     

New Sphingolipids with a Previously Unreported 9-Methyl-C<Subscript>20</Subscript>-sphingosine Moiety from a Marine Algous Endophytic Fungus <Emphasis Type="Italic">Aspergillus niger</Emphasis> EN-13

Asperamides A (1) and B (2), a sphingolipid and their corresponding glycosphingolipid possessing a hitherto unreported 9-methyl-C₂₀-sphingosine moiety, were characterized from the culture extract of Aspergillus niger EN-13, an endophytic fungus isolated from marine brown alga Colpomenia sinuosa. The structures were elucidated by spectroscopic and chemical methods as (2S,2′R,3R,3′E,4E,8E)-N-(2′-hydroxy-3′-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (1) and 1-O-β-d-glucopyranosyl-(2S,2′R,3R,3′E,4E,8E)-N-(2′-hydroxy-3′-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (2). In the antifungal assay, asperamide A (1) displayed moderate activity against Candida albicans.     

Antibacterial and xanthine oxidase inhibitory cerebrosides from <Emphasis Type="Italic">Fusarium</Emphasis> sp. IFB-121, and endophytic fungus in <Emphasis Type="Italic">Quercus variabilis</Emphasis>

Two antibacterial and xanthine oxidase inhibitory cerebrosides, one of which is chemically new, were characterized from the chloroform-methanol (1∶1) extract of Fusarium sp. IFB-121, an endophytic fungus in Quercus variabilis. By means of chemical and spectral methods [IR, electrospray ionization MS (ESI-MS), tandem ESI-MS, ¹H and ¹³C NMR, distortionless enhancement by polarization transfer, COSY, heteronuclear multiple-quantum coherence, heteronuclear multiple-bond correlation, and 2-D nuclear Overhauser effect correlation spectroscopy], the structure of the new metabolite named fusaruside was established as (2S,2′R,3R,3′E,4E,8E,10E)-1-O-β-d-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8,10-sphingatrienine, and the structure of the other was identified as (2S,2′R,3R,3′E,4E,8E)-1-O-β-d-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8-sphingadienine. Both new and known cerebrosides, although inactive to Trichophyton rubrum and Candida albicans, showed strong antibacterial activities against Bacillus subtilis, Escherichia coli, and Pseudomonas fluorescens, with their minimum inhibitory concentrations being 3.9, 3.9, and 1.9 μg/mL, and 7.8, 3.9, and 7.8 μg/mL, respectively. Furthermore, both metabolites were inhibitory to xanthine oxidase, with the IC₅₀ value of fusaruside being 43.8±3.6 μM and the known cerebroside being 55.5±1.8 μM.     

Binary phase behavior of 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS) and 1,3-distearoyl-2-linoleoyl-sn-glycerol (SLS)

The binary phase behavior of SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SLS (1,3-distearoyl-2-linoleoyl-sn-glycerol) was examined by using DSC and conventional and synchrotron radiation X-ray diffraction. The solid-solution phases were observed in the metastable α and γ forms in all concentration ranges. Results indicated that the miscible γ form did not transform to the β′ form when the mixtures were subjected to simple cooling from a high-temperature liquid to a low-temperature solid phase. However, and α-melt-mediated transformation into β′ and β₂ resulted in the formation of immiscible phases in concentration ranges of SLS below 30%. By contrast, at SLS concentration ranges above 30%, the α-melt-mediated transformation caused crystallization of only the γ form, and β′ and β₂ crystals did not appear. These results show that the specific interactions between SOS and SLS are operative in the phase behavior of the mixture states of SOS and SLS.     

Synthesis and Antioxidancy of Some <Emphasis Type="Italic">n</Emphasis>-Alkyl, <Emphasis Type="Italic">t</Emphasis>-Alkyl,Homologous and Isomeric Lipidic Alkylthiobisphenols

To study the relationship between structure and properties of members of the lipidic thiobis phenol series, as extreme pressure additives in lubricants, a series of homologous compounds has been synthesised by the reaction of alkylphenols with sulphur dichloride. The isomeric n-nonylphenols have been reacted to form the C9 isomeric 2,2′-and 4,4′-thiobisphenols. Longer alkyl side-chains resulted mainly in the formation of 4,4′-thiobisphenols and some of the 2,2′ isomer. With short alkyl, particularly t-alkyl side-chains, steric hindrance resulted in the 2,2′-compound. Additive studies have indicated that the longer chain 4,4′ compounds possessed antioxidant properties comparable and superior to former commercial branched chain 2,2′ compounds produced from petrochemical intermediates. Lipidic alkylthiobisphenols: Long chain phenols, Part 40b (Part 40a, ref 6).     

Structural investigations of β′ triacylglycerols: An x-ray diffraction and microscopic study of twinned β′ crystals

To reveal the structure ofβ′ triacylglycerols in detail, LML (C₁₂C₁₄C₁₂) was purified by a zone-melting procedure, and twinned crystals ofβ′ stable LML were obtained from a melt,β′ LML crystallizes in the monoclinic space group C₂, with eight molecules in the unit cell. A powder X-ray diffraction study of solid compounds of 1:1 mixtures of selected triacylglycerols led to the conclusion that the triacylglycerol molecules in theβ modification have a 1,2 chair-conformation (i.e., the fatty acid chains on glycerol positions 1 and 2 are adjacent, with the chain on the 3-position forming the back rest of the chair). Packing studies and the positions of two-fold axes and two-fold screw axes in the unit cell require that the molecules are bent at the glycerol site. The fatty acid chains make an angle of 25° with the long axis of the unit cell. Electron micrographs and precession photographs indicate that the twinning results from the stacking of a large number of thin crystalline platelets in two distinct orientations.     

Polymorphism of POP and SOS. I. occurrence and polymorphic transformation

The polymorphic modifications of POP and SOS were identified with X-ray diffraction (XRD), DSC and Raman spectroscopy by using pure samples (99.9%). In POP, six polymorphs, α,γ, pseudo-β′₂, pseudo-β′₁, β′₂ and β′₁, were obtained, whereas five polymorphs, α, γ, pseudo-β′, β₂ and β₁, were isolated in SOS. Thermodynamic stability increased from α to β₁ straightforwardly both in POP and SOS, because the polymorphic transformation went monotropically in the order described above. Additionally, the 99.2% sample of POP crystallized another form, δ, but the 99.9% sample did not, implying subtle influences of the impurity. The four forms, α, γ, β₂ and β₁, of POP, revealed XRD and DSC patterns identical to the four forms of SOS designated by the same symbols. The chain length structure was double inα and triple in the other three forms in both POP and SOS. Peculiarity of POP was revealed partly in the chain length structure of pseudo-β′₂ and pseudo-β′₁ which were double, whereas pseudo-β′ of SOS was triple. This apparently showed contrast to the facts that the three forms revealed rather similar XRD short spacing patterns. Another peculiarity of POP was revealed in enthalpy value of the melt crystallization of α: ΔH_c (α) = 68.1 kJ/mol which was much larger than that of SOS (47.7 kJ/mol), and also than AOA and BOB. These peculiarities mean that the double chain length structures of POP are more stabilized than the others. Raman bands of CH₂ scissoring mode of SOS indicated parallel packing in γ, β₂ and β₁, and orthorhombic perpendicular packing in pseudo-β′. The polymorphic transformation mechanisms were discussed based on the proposed polymorphic structure models. Presented at the AOCS annual meetings in New Orleans, Louisiana in May 1987 and Phoenix, Arizona in May 1988.     

Evidence for multiple sterol methyl transferase pathways in <Emphasis Type="Italic">Pneumocystis carinii</Emphasis>

The sterol composition of Pneumocystis carinii, an opportunistic pathogen responsible for life-threatening pneumonia in immunocompromised patients, was determined. Our purpose was to identify pathway-specific enzymes to impair using sterol biosynthesis inhibitors. Prior to this study, cholesterol 15 (ca. 80% of total sterols), lanosterol 1, and several phytosterols common to plants (sitosterol 31, 24α-ethyl and campesterol, 24α-methyl 30) were demonstrated in the fungus. In this investigation, we isolated all the previous sterols and many new compounds from P. carinii by culturing the microorganism in steroid-immunosuppressed rats. Thirty-one sterols were identified from the fungus (total sterol=100 fg/cell), and seven sterols were identified from rat chow. Unusual sterols in the fungus not present in the diet included, 24(28)-methylenelanosterol 2; 24(28)E-ethylidene lanosterol 3; 24(28)Z-ethylidene lanosterol 4; 24β-ethyllanosta-25(27)-dienol 5; 24β-ethylcholest-7-enol 6; 24β-ethylcholesterol 7; 24β-ethylcholesta-5,25(27)-dienol 8; 24-methyllanosta-7-enol 9; 24-methyldesmosterol 10; 24(28)-methylenecholest-7-enol 11; 24β-methylcholest-7-enol 12; and 24β-methylcholesterol 13. The structural relationships of the 24-alkyl groups in the sterol side chain were demonstrated chromatographically relative to authentic specimens, by MS and high-resolution ¹H NMR. The hypothetical order of these compounds poses multiple phytosterol pathways that diverge from a common intermediate to generate 24β-methyl sterols: route 1, 1→2→11→12→13; route 2, 1→2→9→10→13; or 24β-ethyl sterols: route 3, 1→2→4→6→7; route 4, 1→2→5→8→7. Formation of 3 is considered to form an interrupted sterol pathway. Taken together, operation of distinct sterol methyl transferase (SMT) pathways that generate 24β-alkyl sterols in P. carinii with no counterpart in human biochemistry suggests a close taxonomic affinity with fungi and provides a basis for mechanism-based inactivation of SMI enzyme to treat Pneumocystis pneumonia.     

Molecular characterization of three peroxisome proliferator-activated receptors from the sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>)

Peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that control the expression of genes involved in lipid homeostasis in mammals. We searched for PPAR in sea bass, a marine fish of particular interest to aquaculture, after hypothesizing that the physiological and molecular processes that regulate lipid metabolism in fish are similar to those in mammals. Here, we report the identification of complementary DNA and corresponding genomic sequences that encode three distinct PPAR from sea bass. The sea bass PPAR are the structural homologs of the mammalian PPARα, β/δ and γ isotypes. As revealed by RNase protection, the tissue expression profile of the fish PPAR appears to be very similar to that of the mammalian PPAR homologs. Thus, PPARα is mainly expressed in the liver, PPARγ in adipose tissue, and PPARβ in all tissues tested, with its highest levels in the liver, where it is also the dominant isotype expressed. Like mammalian PPAR, the sea bass isotypes recognize and bind to PPAR response elements of both mammalian and piscine origin, as heterodimers with the 9-cis retinoic acid receptor. Through the coactivator-dependent receptor ligand assay, we also demonstrated that natural FA and synthetic hypolipidemic compounds can act as ligands of the sea bass PPARα and β isotypes. This suggests that the sea bass PPAR act through similar mechanisms and perform the same critical lipid metabolism functions as mammalian PPAR.     

Further studies on sphingolipids in wheat grain

The principal molecular species of sphingolipids in wheat grain were confirmed to beN-2′-hydroxylignoceroyl-4-hydroxysphinganine for ceramide, and 1-O-β-glucosyl-, 1-O-[β-mannosyl(1→4)-O-β-glucosyl]-, 1-O-[β-mannosyl(1→4)-O-β-mannosyl(1→4)-O-β-glucosyl]-and 1-O[β-mannosyl(1→4)-O-β-mannosyl(1→4)-O-β-mannosyl(1→4)-O-β-glucosyl]-N-2′-hydroxypalmitoyl (or hydroxyarachidoyl)-cis-8-sphingenine for mono-, di-, tri- and tetraglycosylceramide, respectively. A novel glycolipid, cellobiosylceramide, was found as the minor diglycosylceramide; the major species was characterized to be 1-O-[β-glucosyl(1→4)-O-β-glucosyl]-N-2′-hydroxypalmitoyl (or hydroxyarachidoyl)-cis-8-sphingenine. It was observed in these sphingolipids that the dihydroxy bases were combined mainly with C₁₆ and C₂₀ acids, whereas the trihydroxy bases combined mostly with acids of chain length of 20 or more.     

Physical properties of Pseudomonas and Rhizomucor miehei lipase-catalyzed transesterified blends of palm stearin:palm kernel olein

The physical properties of Pseudomonas and Rhizomucor miehei lipase-catalyzed transesterified blends of palm stearin:palm kernel olein (PS:PKO), ranging from 40% palm stearin to 80% palm stearin in 10% increments, were analyzed for their slip melting points (SMP), solid fat content (SFC), melting thermograms, and polymorphic forms. The Pseudomonas lipase caused a greater decrease in SMP (15°C) in the PS:PKO (40:60) blend than the R. miehei lipase (10.5°C). Generally, all transesterified blends had lower SMP than their unreacted blends. Pseudomonas lipase-catalyzed blends at 40:60 and 50:50 ratio also showed complete melting at 37°C and 40°C, respectively, whereas for the R. miehei lipase-catalyzed 40:60 blend, a residual SFC of 3.9% was observed at 40°C. Randomization of fatty acids by Pseudomonas lipase also led to a greater decrease in SFC than the rearrangement of fatty acids by R. miehei lipase. Differential scanning calorimetry results confirmed this observation. Pseudomonas lipase also successfully changed the polymorphic forms of the unreacted blends from a predominantly β form to that of an exclusively β′ form. Both β and β′ forms existed in the R. miehei lipase-catalyzed reaction blends, with β′ being the dominant form.