Green S M, Malik T, Giles I G, Drabble W T
Department of Biochemistry, University of Southampton, Crescent East, UK.
Microbiology (Reading). 1996 Nov;142 ( Pt 11):3219-30. doi: 10.1099/13500872-142-11-3219.
The structural gene (purB) for succinyl-AMP (S-AMP) lyase and three additional ORFs are on the same DNA strand of the chromosome of Escherichia coli. Cassette mutagenesis and primer extension mapping demonstrated that purB is co-transcribed with an upstream gene (ORF23, or ycfC) encoding a 22.9 kDa membrane-associated protein of non-essential, but unknown, function unrelated to purine biosynthesis. The purB operon lies between phoP and an ORF expressing an essential function which may correspond to asuE (trmU). S-AMP lyase was purified to near homogeneity. The purified enzyme is a homotetramer of 50 kDa subunits, has a K(m) for S-AMP of 3.7 microM and a pH optimum of 7.4-7.6.
琥珀酰 - AMP（S - AMP）裂解酶的结构基因（purB）以及另外三个开放阅读框（ORF）位于大肠杆菌染色体的同一条DNA链上。盒式诱变和引物延伸图谱分析表明，purB与上游基因（ORF23，即ycfC）共同转录，该上游基因编码一种22.9 kDa的膜相关蛋白，其功能非必需且未知，与嘌呤生物合成无关。purB操纵子位于phoP和一个表达必需功能的ORF之间，该ORF可能对应于asuE（trmU）。S - AMP裂解酶被纯化至接近均一。纯化后的酶是由50 kDa亚基组成的同四聚体，对S - AMP的K(m)为3.7 microM，最适pH为7.4 - 7.6。
