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B6db references: 18952881

type Journal Article
authors Nozaki, H.; Kuroda, S.; Watanabe, K.; Yokozeki, K.
title Purification and Gene Cloning of {alpha}-Methylserine Aldolase from Ralstonia sp. AJ110405 and its Application in the Enzymatic Synthesis of {alpha}-Methyl-l-serine
journal Appl Environ Microbiol
Activity metser.aldolase
Family metser.aldolase
sel selected
ui 18952881
year (2008)
volume 74
pages 7596-9
abstract By screening microorganisms that are capable of assimilating alpha-methyl-dl-serine, we firstly detected alpha-methylserine aldolase in Ralstonia sp. AJ110405, Variovorax paradoxus AJ110406, and Bosea sp. AJ110407. The enzyme was purified in a homogeneous form from Ralstonia sp. AJ110405, and the corresponding gene was cloned and expressed in Escherichia coli. The enzyme appeared to be a homodimer, consisting of identical subunits, and its molecular mass was found to be 47 kDa. It contained 0.7-0.8 mol of pyridoxal 5'-phosphate (PLP) per mole of a subunit and could catalyze the interconversion of alpha-methyl-l-serine to l-alanine and formaldehyde in the absence of tetrahydrofolate (THF). Formaldehyde was generated from alpha-methyl-l-serine but not from alpha-methyl-d-serine, l-serine, or d-serine. The synthesis activity of alpha-methyl-l-serine was detected when l-alanine was used as the substrate. In contrast, no activity was detected when d-alanine was used as the substrate. In the alpha-methyl-l-serine synthesis reaction, the enzymatic activity was inhibited by an excess amount of formaldehyde, which was one of the substrates. We used the cells of E. coli as a whole-cell catalyst to express the gene encoding alpha-methylserine aldolase and effectively obtained a high yield of optically pure alpha-methyl-l-serine from l-alanine and formaldehyde.
last changed 2009/01/08 13:32

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