Antibody against pulmonary surfactant protein A recognizes proteins in intestine and swim bladder of the freshwater fish, carp

An antibody raised against rat pulmonary surfactant protein A (SP-A) bound on Western blots to proteins present in intestinal mucosa and in swim bladder, but not in gills of the carp. The fish protein(s) revealed by the antibody exhibited an electrophoretical behavior similar to that of rat SP-A with a characteristic triplet in the 30- to 35-kDa range. It therefore appears that proteins immunologically very close to mammalian SP-A are present in modern fish which evolved from ancestors that never possessed lungs. The association of SP-A with phospholipid-rich surfactant-like materials appears as a phylogenetically old feature.     

Enantioselective, mechanism-based inactivation of guinea pig hepatic cytochrome P450 by N-(alpha-methylbenzyl)-1-aminobenzotriazole

N-Aralkylated derivatives of 1-aminobenzotriazole are well-established, mechanism-based inhibitors of cytochrome P450 (CYP or P450). In this study, the kinetics of inactivation of CYP2B-dependent 7-pentoxyresorufin O-depentylation (PROD) and CYP1A-dependent 7-ethoxyresorufin O-deethylation (EROD) activities by enantiomers of N-(alpha-methylbenzyl)-1-aminobenzotriazole (alphaMB) were compared. The racemic mixture (+/-)-alphaMB, as well as the enantiomers (-)-alphaMB and (+)-alphaMB, produced a time-, concentration-, and NADPH-dependent loss of PROD and EROD activity in hepatic microsomes from phenobarbital-treated guinea pigs. The rates of PROD inactivation by (-)-alphaMB were significantly faster than for (+)-alphaMB. Consistent with this, the derived maximal kinact was also significantly greater for (-)-alphaMB than for (+)-alphaMB (0.49 vs. 0.35 min-1). In contrast, the concentrations required for the half-maximal rate of inactivation (Ki) were equivalent for (-)-alphaMB and (+)-alphaMB, whereas the degree of competitive inhibition of PROD activity was greater for (+)-alphaMB. No significant differences were found among (-)-alphaMB, (+)-alphaMB, and (+/-)-alphaMB with respect to mechanism-based inactivation (kinact = 0.18, 0.16, and 0.17 min-1, respectively) or competitive inhibition of EROD activity. No differences were found for the maximal extent of PROD or EROD inhibition or the loss of spectral P450 after an extended 30-min incubation with the inhibitors. We conclude that mechanism-based inactivation of guinea pig CYP2B, but not CYP1A, isozymes by alphaMB occurs in a stereoselective manner, most likely as a result of a difference in the balance between metabolic activation and deactivation for the alphaMB enantiomers.     

Biodegradation pathway of 2-chlorodibenzo-p-dioxin and 2-chlorodibenzofuran in the biphenyl-utilising strain JB1

The biphenyl-utilising Burkholderia (previously Alcaligenes) strain JB1 is also able to degrade a number of chlorinated dibenzo-p-dioxins and dibenzofurans. In this study, 4-chlorocatechol and a chlorotrihydroxydiphenyl ether were identified as metabolites of 2-chlorodibenzo-p-dioxin. 5-Chlorosalicylic acid and a chlorotrihydroxybiphenyl were metabolites of 2-chlorodibenzofuran. These results show that degradation of these compounds follows pathways in which the initial reaction is angular dioxygenation, followed by cleavage of an ether bridge. This pathway is similar to that used by dibenzofuran-degrading strains such as Sphingomonas sp. strain RW1.