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MALIC DEHYDROGENASES FROM DIOSCOREA ROTUNDATA TUBERS: PURIFICATION AND PROPERTIES OF TWO ISOZYMES
Author(s) -
NOK A.J.,
UKOHA A.I.,
IKEDIOBI C.O.,
AKANYA H.O.
Publication year - 1991
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.1991.tb00426.x
Subject(s) - dioscorea rotundata , isozyme , dioscorea , malate dehydrogenase , malic acid , biology , chemistry , botany , food science , biochemistry , enzyme , medicine , alternative medicine , pathology , citric acid
Two molecular forms of the enzyme malate dehydrogenase (MDH 1 and MDH 2 ) have been purified from Dioscorea rotundata tubers. The enzymes were resolved on a DEAE‐cellulose column and found to be homogeneous with differential mobilities on polyacrylamide gels. Both enzymes appeared to be dimeric proteins with subunit molecular weights of 30, 100 ± 50 and 31,600 ± 250 for MDH 1 and MDH 2 , respectively. The enzymes exhibited maximal catalytic activity within the pH range 6.57.5 at 37C and were inhibited by oxaloacetic acid at concentrations greater than 0.25 mM as well as other naturally occurring metabolites (citric acid, isocitric acid, a‐hetoglutaric acid, succinic acid, pyruvic acid, aspartic acid, glutamic acid, ATP and ADP). The thermal stability and storability of the enzymes at different conditions were significantly different.