Structure/function analysis of abundance and transmission mechanism of genetic information invlolved in the biosynthesis of multi-catalytic site enzyme

胞内藻酸盐裂解酶I、II和III由一个基因编码，并通过顺序翻译后反应从共同的前体蛋白Po产生：Po → I + 5 kDa肽，I → II +III。酶Ⅰ的蛋白酶样活性可被EDTA或邻菲咯啉完全抑制，表明酶Ⅰ是一个多催化位点酶，催化Ⅱ、Ⅲ和蛋白酶。I上的蛋白酶位点被认为是通过从Po切除N-末端5 kDa肽而产生的，因为Po没有蛋白酶活性。然后提出了一个重要的生物学问题，即蛋白酶位点是如何产生的，以及这些信息是如何/在哪里在碱基和氨基酸序列中描述的。这些地址的澄清可能会导致一个新的理论关于丰富的信息包含在一个基因的假设。为了解决这些问题，需要了解海藻酸裂解酶I、II和III及其前体蛋白Po的结构/功能关系。其中，III的结构/功能通过X-射线晶体学进行了全面分析，并阐明了详细的裂解酶反应机理。特别地，以低垒氢键理论为重点，构建了一个新的涉及Tyr残基而非His残基的β-消除反应机理。

The intracellular alginate lyases I,II, and III are coded by one gene and produced through sequential post-translational reactions from a common pre-cursor protein Po : Po → I + 5 kDa peptide, I → II +III. The protease-like activity of I is completely inhibited by EDTA or O- phnonthroline, thus indicates that the I is a multi- catalytic site enzyme currying II, III, and protease. The protease site on I is thought to be created through the excision of N-terminal 5 kDa peptide from Po, since Po has no protease activity. An important biological problem is then raised as to how the protease site is generated and how / where the information is described in the base and amino acid sequences. The clarification of these addresses may lead to the postulation of a novel theory concerning the abundance of information contained in a gene. To solve the problems, the knowleges on the structure / function relationship of alginate lyases I, II, and III, as well as their precursor protein Po. Among these, the structure / function of III was completely analyzed through X-ray crystallography and detailed lyase reaction mechanism was clarified. Especially, a novel β-elimination reaction mechanism involving Tyr residue, but not His, was constructed with an emphasis of Low-Barrier Hydrogen Bond Theory.