Archaebacterial malate dehydrogenase: the amino-terminal sequence of the enzyme from Sulfolobus acidocaldarius is homologous to the eubacterial and eukaryotic malate dehydrogenases.

42 residues of the N-terminal amino acid sequence of malate dehydrogenase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius have been determined as VKVAFIGVGRGVGQTIAYNTIVNGYADEVMLYDVVPELPTKK. In eubacterial and eukaryotic enzymes this region is known to encompass residues involved in pyridine nucleotide binding. In the archaebacterial enzyme the residues Gly-7, Gly-11 and Asp-33 are also present. The data suggest that in the enzyme from S. acidocaldarius like in the other malate dehydrogenases the binding domain for NAD(H) is localized at the N-terminal part of the polypeptide chain. The archaebacterial enzyme is homologous to the other malate dehydrogenases, of which the amino acid sequences are known, however, it is only distantly related to the mitochondrial/E. coli group and the cytosolic/Thermus flavus group.