HEME BIOSYNTHESIS--C5 PATHWAY TO 5 AMINOLEVULINATE

大肠杆菌中血红素的生物合成 血红素及其相关的环状四吡咯是 血红蛋白、细胞色素、过氧化物酶、叶绿素和维生素B12。 环四吡咯生物合成途径中的许多步骤 是高度保守的。 该途径，必然是在光代谢 控制 各种生物体中的一些控制机制是 正在调查中 在克隆和测序两个 基因的血红素生物合成途径hemA和hemB，我们证明了一个 控制胆色素原脱氨酶活性的独特机制 （PBG-D），该途径中的关键酶，即hemB的表达， 是PBG-D活性所必需的。 此外，我们积极 研究参与基因表达的控制， 合成途径的第一个定向中间体，5- 氨基乙酰丙酸（ALA）。 我们阐明了生物合成途径 ALA在E.大肠杆菌，并通过生化和遗传技术表明， ALA是由C5途径产生的，而不是像以前那样由C4途径产生。 相信。 我们还鉴定和表征了血红素突变体， 正在进行克隆和测序。我们过度表达了 hemB是ALA脱氢酶的结构基因， 酵素 建议克隆血红素的其余未克隆基因 在E.大肠杆菌，并通过体内和体外技术进行研究， 血红素的控制（转录、翻译和酶） 生物合成途径

Heme Biosynthesis in Escherichia coli Heme and its related cyclic tetrapyrroles are the prosthetic groups of the hemoglobins, cytochromes, peroxidases, chlorophylls and Vitamin B12. Many of the steps in the biosynthetic pathway of the cyclic tetrapyrroles are highly conserved. The pathway, by necessity is under light metabolic control. Some of the mechanisms of control in various organisms are under active investigation. In the process of cloning and sequencing two genes of the heme biosynthetic pathway hemA and hemB, we demonstrated a unique mechanism of control of the activity of porphobilinogen deaminase (PBG-D), a key enzyme in the pathway, namely that the expression of hemB is required for the activity of PBG-D. In addition, we are actively investigating the control of expression of the genes involved in the synthesis of the first committed intermediate of the pathway, 5- aminolevulinic acid (ALA). We elucidated the pathway of the biosynthesis of ALA in E. coli and showed by both biochemical and genetic techniques that ALA is made by the C5 pathway and not by the C4 as previously believed. We have also identified and characterized a hemE mutant and are in the process of cloning and sequencing it. We have over-expressed hemB, the structural gene for ALA dehydratase and characterized this enzyme. It is proposed to clone the rest of the uncloned genes of heme biosynthesis in E. coli and to study by in vivo and in vitro techniques, the control (transcriptional, translational and enzymatic) of the heme biosynthesis pathway.