A family of highly conserved glycosomal 2-hydroxyacid dehydrogenases from Phytomonas sp.

UTTARO, A; ALTABE, SILVIA GRACIELA; RIDER, M; MICHELS, P; OPPERDOES, F

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Baltimore MD; Año: 2000 vol. 275 p. 31833 - 31837

0021-9258

Phytomonas sp. contains two malate dehydrogenase isoforms, a mitochondrial isoenzyme with a high specificityfor oxaloacetate and a glycosomal isozyme that acts on a broad range of substrates (Uttaro, A. D., and Opperdoes, F.R. (1997) Mol. Biochem. Parasitol. 89, 51–59). Here, we show that the low specificity of the latter isoenzyme is the result of a number of recent gene duplications that gave rise to a family of glycosomal 2-hydroxyacid dehydrogenase genes. Two of these genes were cloned, sequenced, and overexpressed in Escherichia coli. Although both gene products have 322 aminoacids, share 90.4% identical residues, and have a similar hydrophobicity profile and net charge, their kinetic properties were strikingly different. One isoform behaved as a real malate dehydrogenase with a high specificity for oxaloacetate, whereas the other showed no activity with oxaloacetate but was able to reduce other oxoacids, such as phenyl pyruvate, 2-oxoisocaproate, 2-oxovalerate, 2-oxobutyrate, 2-oxo-4-methiolbutyrate,and pyruvate.