Serine hydroxymethyltransferase (SHMT) plays a key role in cell physiology as it participates in the different interconversion pathway of folate coenzymes, provides almost exclusively folate one carbon fragments for the biosynthesis of a variety of end products. For the first time, Mycobacterium leprae glyA gene, encodes the enzyme serine hydroxymethyltransferase, has been cloned in Escherichia coli, over-expressed and purified the protein product (m/SHMT) for folding and stability studies under various denaturating conditions. The recombinant m/SHMT exists as homo-dimer of molecular mass about 90 kDa under physiological conditions. The studies on catalytic properties of m/SHNIT show that the enzyme catalyzes the H-4-folate dependent retro-aldol cleavage Of L-serine, however, D-alanine dependent transaminase activity was absent in the enzyme. Further analysis of the enzyme kinetics for hydroxymethyltransferase reaction for m/SHMT demonstrates a comparable K,, value for L-serine to SHMTs from other sources but significantly lower catalytic efficiency (k(cat)/K-m). The m/SHNIT is resistant to alkaline denaturation and exist as apo-dimer up to pH 10.5. Urea and guanidinium chloride induces dissociation of m/SHMT dimer into monomer at low denaturant concentrations, and leads to loss of enzymatic activity. (C) 2007 Elsevier Inc. All rights reserved.