Proteolytic activation of grass carp (Ctenopharygodon idellus) liver alcohol dehydrogenase.
Two different forms of alcohol dehydrogenase (ADH) were prepared from the liver of grass carp, using ion-exchange chromatography on DEAE-cellulose and affinity chromatography on Affi-gel Blue agarose. In the presence of dithiothreitol and benzamidine. ADH-l, a dimeric protein with native molecular weight of 80 kDa, was obtained. However, in their absence, another form of the enzyme, ADH-C, consisting of two 27 kDa and two 13 kDa subunits tightly but non-covalently associated with each other, can be isolated. ADH-C represented a cleaved form of the enzyme and was shown to be derived from the original, intact form, ADH-l through limited and specific proteolytic cleavage. Surprisingly, such a cleavage caused an activation of the enzyme toward the oxidation of ethanol at pH 10.5. The Vmax value of ADH-C was 5.16-fold greater than that of ADH-l. However, ADH-C had much weaker binding affinity for the alcohol. Its Km value toward ethanol was 163-fold higher than that of ADH-l.
Tsui
H T
HT
Department of Biochemistry, Chinese University of Hong Kong, Shatin.
Mock
W Y
WY
Lau
K K
KK
Fong
W P
WP
D000426:Alcohol Dehydrogenase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002347:Carps / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004789:Enzyme Activation; D007700:Kinetics; D008099:Liver / Q000737:chemistry / Q000201:enzymology*; D008970:Molecular Weight
D000426:Alcohol Dehydrogenase