Molina I, Pellicer M T, Badia J, Aguilar J, Baldoma L
Department of Biochemistry, School of Pharmacy, University of Barcelona, Spain.
Eur J Biochem. 1994 Sep 1;224(2):541-8. doi: 10.1111/j.1432-1033.1994.00541.x.
Two genes encoding the enzymes malate synthase G and glycolate oxidase, have been linked to locus glc (64.5 min), responsible for glycolate utilization in Escherichia coli. The gene encoding malate synthase G, for which we propose the notation glcB, has been cloned, sequenced and found to correspond to a 2262-nucleotide open-reading frame, which can encode a 723-amino-acid polypeptide, clearly different from the isoenzyme malate synthase A, which has 533 amino acids. Northern-blot experiments indicate that glcB was expressed as an apparently monocistronic transcript, inducible by glycolate. Malate synthase G was purified to near homogeneity. The molecular mass determined by gel filtration yielded a value of 82 kDa for the purified enzyme and the same value as for the crude extract enzyme, indicating a monomeric structure. Despite the lower sequence similarity between malate synthase G and the other reported malate synthases, three out of nine consensus boxes defined in most of these enzymes are conserved in addition to a cysteine residue that has been reported to be important for the catalytic mechanisms.
编码苹果酸合酶G和乙醇酸氧化酶的两个基因，已与大肠杆菌中负责乙醇酸利用的glc位点（64.5分钟处）相关联。编码苹果酸合酶G的基因，我们提议将其命名为glcB，已被克隆、测序，发现它对应于一个2262个核苷酸的开放阅读框，该阅读框可编码一个723个氨基酸的多肽，明显不同于具有533个氨基酸的同工酶苹果酸合酶A。Northern印迹实验表明，glcB以明显的单顺反子转录本形式表达，可被乙醇酸诱导。苹果酸合酶G被纯化至接近均一。通过凝胶过滤测定的纯化酶的分子量为82 kDa，与粗提物酶的值相同，表明其为单体结构。尽管苹果酸合酶G与其他已报道的苹果酸合酶之间的序列相似性较低，但除了一个据报道对催化机制很重要的半胱氨酸残基外，在大多数这些酶中定义的九个共有框中的三个是保守的。
