新辅基吡咯喹啉醌(PQQ)生物合成基因研究进展

Progress in the Biosynthesis Gene of a New Prosthetic Group Pyrroloquinoline Quinone

吡咯喹啉醌（Ｐｙｒｏｌｏｑｕｉｎｏｌｉｎｅ－Ｑｕｉｎｏｎｅ，ＰＱＱ）是氧化还原酶的新辅基。它在细菌体内是由一组排列成簇的相关基因即ｐｑｑ基因控制合成的。根据不同细菌来源ｐｑｑ基因的同源性和对应关系，可将ｐｑｑ基因归为７类：簇基因１～７。在Ａｃｉｎｅｔｏｂａｃｔｅｒｃａｌｃｏａｃｅｔｉｃｕｓ中存在其中四个，ＫｌｅｂｓｉｅｌａＰｎｅｕｍｏｎｉａｅ和ＭｅｔｈｙｌｏｂａｃｔｅｒｉｕｍＯｒｇａｎｏｐｈｉｌｕｍＤＳＭ７６０中６个，而Ｍｅｔｈｙｌｏｂａｃｔｅｒｉｕｍｅｘ－ｔｏｒｑｕｅｎｓＡＭ１中存在全部７个簇基因。簇基因１编码一个由２２～２９年氨基酸组成的小肽，此小肽可能是ＰＱＱ的前体，簇基因２可能涉及ＰＱＱ跨膜转运，簇基因３可能负责ＰＱＱ合成的最后一步酶催化，簇基因５可能涉及ＰＱＱ合成中某种酶的辅因子合成，簇基因６和７可能负责小肽的加工。簇基因４功能还不清楚，但在Ｍ．ｅｘｔｏｒｑｕｅｎｓＡＭ１中簇基因３和４是以融合基因存在的。

pyrroloquinoline quinone (PQQ) is a new prostheric group of oxidoreductases. The biosynthesis of PQQis regulated by pqq gene clusters in bacteria, which are designated clusted gene 1-7 by their similarities. There are 4、6、6 and 7 clusted genes in Acinetobacter calcoaceticus, Klebsiella pneumoniae, Methylobacterium organophilum DSM760 and Methylobacterium extorquens AM 1, respectively. Clusted gene 1 encodes a peptide containing 22-29 amino acids which is probably the precursor of PQQ. Clusted gene 2 probably is involved in the cross membrane transportation of PQQ. The product of Clusted gene 3 probably catalyzes the last step of PQQ biosynthesis. Chusted gene 5 appears to be involved in the synthesis of a cofactor, and clusted gene 6 and 7 are proposed to be involved in the process of small peptides. It is not clear about the function of clusted gene 4. Clusted gene 3 is fused with gene 4 in M.extorquens AM 1.