A cDNA which encodes for zebrafish serine hydroxymethyltransferase (SHMT) has been cloned into a pET43.Ia vector as a NdeI-EcoRl insert and transformed into HMS174(DE3) cells. After induction with isopropyl thiogalactoside, the enzyme was purified with a three-step purification protocol and about 15 mg of pure enzyme was obtained per liter of culture. Spectral and structural characteristics of the recombinant zebrafish SHMT are similar to the rabbit and human cytosolic SHMT. Kinetic constants for the natural substrates (L)-serine and tetrahydrofolate are also comparable to the values obtained previously for the rabbit and human cytosolic enzyme. (c) 2005 Elsevier Inc. All rights reserved.