Heme metabolism enzymes are dynamically expressed during <i>Xenopus</i> embryonic development

As the key component of many hemoproteins (heme-containing proteins), heme is involved in a broad range of biological processes. Enzymes required for heme biosynthesis and degradation pathways are evolutionarily conserved. While heme metabolism has been studied extensively, the expression of heme metabolism enzymes during development has not been described. Here, we report that all heme biosynthases and two heme oxygenases, which initiate heme degradation, are dynamically expressed during Xenopus embryonic development. All heme synthases, with the exception of aminolevulinic acid synthase 2, are maternally expressed. At neurula stage, heme synthases are expressed in the developing neural tissue and in migrating neural crest cells. At the swimming tadpole stage, expression of heme synthases can be detected in multiple lineages, including eyes, neural crest cells, developing central nervous system, ventral blood island, pronephron, and pronephric tubule. Similar to heme synthases, heme oxygenases are expressed maternally. Zygotic expression of heme oxygenases is mainly restricted to the developing neural and neural crest lineages. Unlike heme synthases, heme oxygenases are not expressed in the ventral blood island and are expressed at a very low level in the pronephron and pronephric tubule. This indicates that heme metabolism may play important roles during development.     

响应面分析法优化血红素提取工艺

在单因素试验的基础上,通过中心组合旋转设计与响应面分析法优化酸性丙酮法提取血红素的工艺,考察浸提时间、酸酮比以及酸性丙酮与血红蛋白的比对血红素得率的影响,并通过响应面分析法得出最佳提取条件。结果表明：最佳提取工艺条件为浸提时间42min、酸酮比3%、酸性丙酮与血红蛋白体积比5.66:1,在此条件下血红素的得率为0.225g/100mL,与预测值0.230g/100mL 相差不显著。     

The Impact of Hypoxia in Early Pregnancy on Placental Cells

Oxygen levels in the placental microenvironment throughout gestation are not constant, with severe hypoxic conditions present during the first trimester. This hypoxic phase overlaps with the most critical stages of placental development, i.e., blastocyst implantation, cytotrophoblast invasion, and spiral artery remodeling initiation. Dysregulation of any of these steps in early gestation can result in pregnancy loss and/or adverse pregnancy outcomes. Hypoxia has been shown to regulate not only the self-renewal, proliferation, and differentiation of trophoblast stem cells and progenitor cells, but also the recruitment, phenotype, and function of maternal immune cells. In this review, we will summarize how oxygen levels in early placental development determine the survival, fate, and function of several important cell types, e.g., trophoblast stem cells, extravillous trophoblasts, syncytiotrophoblasts, uterine natural killer cells, Hofbauer cells, and decidual macrophages. We will also discuss the cellular mechanisms used to cope with low oxygen tensions, such as the induction of hypoxia-inducible factor (HIF) or mammalian target of rapamycin (mTOR) signals, regulation of the metabolic pathway, and adaptation to autophagy. Understanding the beneficial roles of hypoxia in early placental development will provide insights into the root cause(s) of some pregnancy disorders, such as spontaneous abortion, preeclampsia, and intrauterine growth restriction.     

Cobalt Alleviates GA-Induced Programmed Cell Death in Wheat Aleurone Layers via the Regulation of H2O2 Production and Heme Oxygenase-1 Expression

Heme oxygenase-1 (HO-1) and hydrogen peroxide (H₂O₂) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H₂O₂ production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H₂O₂ accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes.     

胰蛋白酶对猪血红蛋白酶解脱色条件优化

以酶解液水解度（hydrolysis degree,DH）、三氯乙酸（trichloroacetic acid,TCA）可溶性氮含量及血红素残留量为评定指标,采用单因素试验比较胰蛋白酶和碱性蛋白酶对猪血红蛋白的酶解脱色效果。在单因素试验基础上,进行4因素3水平正交试验。结果表明：胰蛋白酶水解脱色的效果更好,最佳酶解工艺参数为酶底比7500 U/g、酶解温度45 ℃、pH 7.5、底物质量浓度8 g/100 mL,在此条件下,酶解液DH为25.67%,TCA可溶性氮含量为80.05%,血红素残留量为18.34%,猪血红蛋白多肽粉蛋白含量83.17%;对此条件下制备的猪血红蛋白多肽粉进行分子质量分布分析,分子质量在1 000 Da以下的小肽占比94.20%;最佳酶解脱色条件下,猪血红蛋白多肽粉中TCA可溶性氮含量为80.05%的蛋白占猪血红蛋白多肽粉蛋白含量的96.25%,这与分子质量分布结果比较符合。     

Iron Distribution in Heated Beef and Chicken Muscles

Distribution of iron in six fractions (water-soluble, water-insoluble, diffusate, hematin, total heme, and ferritin) of beef and chicken muscles hcatcd to 55, 70, 85, and 100°C was determined. Iron content decreased in water-soluble fractions and increased in water-insoluble fractions as temperature increased from 27°C to 100°C. Heme iron decreased more from 55°C to 85°C than from 27°C to 55°C or 85°C to 100°C. The increase in diffusate iron appeared to be less than the decrease in heme iron at each heating temperature. As temperature increased from 27°C to 100°C, hematin iron content increased and extractable ferritin iron content decreased. These findings may help explain rapid development of oxidative rancidity in cooked meat.     

Communication Maps: Exploring Energy Transport through Proteins and Water

Frequency-resolved communication maps provide a coarse-grained, global mapping of energy transport channels in a protein as a function of frequency of modes that carry energy. We illustrate the approach with a study of the homodimeric hemoglobin of Scapharca inaequivalvis, which exhibits cooperativity during ligand binding. We compare energy transport between the two hemes of the unliganded and oxygenated protein, which is mediated by water as well as residues forming a hydrogen-bonding network at the interface between the globules, and lies along the pathway for allosteric transitions observed in time-resolved X-ray studies. Non-equilibrium molecular simulations on energy transport from the heme corroborate the energy transport pathways identified by the communication maps.