type	Journal Article
authors	Nozaki H, Kuroda S, Watanabe K, Yokozeki K.
title	Screening of microorganisms producing α-methylserine hydroxymethyltransferase, purification of the enzyme, gene cloning, and application to the enzymatic synthesis of α-methyl-l-serine
journal	J. Mol. Catal. B: Enzym.
Activity	2.1.2.7
Family	2.1.2.7.a
sel	selected
ui	JMolCatal56221
year	(2009)
volume	56
number	4
pages	221-6
keywords	doi: 10.1016/j.molcatb.2008.05.002
abstract	Through the screening of microorganisms capable of utilizing α-methylserine, three representative strains belonging to the bacterial genera Paracoccus, Aminobacter, and Ensifer were selected as potent producers of α-methylserine hydroxymethyltransferase, an enzyme that catalyzes the interconversion between α-methyl-l-serine and d-alanine via tetrahydrofolate. Among these strains, Paracoccus sp. AJ110402 was selected as the strain exhibiting the highest α-methylserine hydroxymethyltransferase activity. The enzyme was purified to homogeneity from a cell-free extract of this strain. The native enzyme is a homodimer with apparent molecular mass of 85 kDa and contains 1 mol of pyridoxal-5′-phosphate per mol of the subunit. The Km for α-methyl-l-serine and tetrahydrofolate was 0.54 mM and 73 μM, respectively. The gene from Paracoccus sp. AJ110402 encoding α-methylserine hydroxymethyltransferase was cloned and expressed in Escherichia coli. Sequence analysis revealed an open reading frame of 1278 bp, encoding a polypeptide with a calculated molecular mass of 46.0 kDa. Using E. coli cells as whole-cell catalysts, 9.7 mmol of α-methyl-l-serine was stereoselectively obtained from 15 mmol of d-alanine and 13.2 mmol of formaldehyde.
last changed	2018/11/22 11:46