Abstract:

The chemical modification of malate dehydrogenase (MDH) with p-chloromercuribenzoate, phenylmethyl sulfonyl
fluoride, N-bromosuccinimide, succinic anhydride, acetylacetone, bromoacetic acid, N-acetylimidazole, dithiothreitol and
chloramine-T showed that the cysteine sulfydryl, tryptophan side chain indole and serine hydroxyl groups involved in the
composition of the enzyme active center could be considered as the essential functional groups of c-MDH and m-MDH from
duck heart. However, the thioether group of methionine, the imidazole group of histidine, the guanidine group of arginine,
disulfide bond, the phenol hydroxyl group of tyrosine and the epsilon-amino group of lysine were not directly related to the
activity of the two MDH enzymes from duck heart, suggesting that they are not essential for the enzyme active center.

Key words: duck heart, malate dehydrogenase (MDH), functional groups, chemical modification