酮古龙酸菌与呼吸链偶联的2-KGA代谢途径研究进展

2-KGA metabolism coupling respiratory chain in Ketogulonigenium vulgare－A review

摘要:

摘要:酮古龙酸菌可将底物L-山梨糖转化为维生素C的前体2-酮基-L-古龙酸(2-KGA)。该菌共存在5种反应参与2-KGA代谢，包括:①D-山梨醇氧化为L-山梨糖;②L-山梨糖氧化为L-山梨酮;③L-山梨酮(吡喃型)氧化为2-KGA;④L-山梨酮(呋喃型)氧化为维生素C。⑤2-KGA还原为L-艾杜糖酸。其中L-山梨糖/L-山梨酮脱氢酶(SSDH)参与反应①②③，L-山梨糖脱氢酶(SDH)参与反应②③，L-山梨酮脱氢酶(SNDH)参与反应③④，醛脱氢酶(ALDH)参与反应③，2-KGA 还原酶(2-KGR)参与反应⑤。SDH/SSDH/ALDH属于Ⅰ型醌酶，其辅酶为1分子PQQ;SNDH属Ⅱ型醌酶，与PQQ、heme C共同构成quinohemoproteins，2种醌酶均分布于周质空间中与呼吸链相偶联，意味着这种膜上直接氧化过程伴随ATP产生，使得菌体可以利用环境中的底物实现快速供能。

Abstract:

Abstract: 2-keto-L-gulonate (2-KGA) is the key intermediate of vitamin C，which can be biosynthesized by Ketogulonigenium vulgare．There are five reactions related to 2-KGA metabolism，including: (1) Oxidation of D-sorbitol to L-sorbose; (2) Oxidation of L-sorbose to L-sorbosone;(3) Oxidation of L-sorbosone (Pyranose form) to 2-KGA; (4) Oxidation of L-sorbosone (Furanose form) to vitamin C，and (5) Reduction of 2-KGA to L-idonate．L-sorbose/Lsorbosone dehydrogenase (SSDH) is responsible for the reaction of 1 through 3，L-sorbose dehydrogenase (SDH) is responsible for the reaction of 2 and 3，L-sorbosone dehydrogenase (SNDH) is responsible for the reaction of 3 and 4，aldehyde dehydrogenase (ALDH) is responsible for the reaction of 3，2-KGA reductase (2-KGR) is responsible for the reaction of 5．Enzymes of SDH，SSDH and ALDH belong to Quinoprotein Type Ⅰ that uses PQQ as the only prosthetic group．SNDH belongs to Quinoprotein Type II that is quinohemoprotein assembling heme c and PQQ．They are all soluble in the periplasm and coupled with the respiratory chain．The substrate respiration to generate ATP directly on the outside cellular membrane means this strain can use the substrate quickly in the natural environment for the necessary bioenergy required．