Abstract
Magnesium stimulation of catalytic activity of horse liver aldehyde dehydrogenase. Changes in molecular weight and catalytic sites.
Highlights
The addition of -0.5 n m M g ’ ions enhancesthe specific activity of the PI 5 isozyme of horse liver aldehyde dehydrogenase by a factor of 2
Assuming that the tetrameric and dimeric forms of the enzyme can function with half-of-sites and all-of-sites reactivities, respectively, we can show that anexcellent correlation exists between theapparent molecular weight and the specific activity of the enzyme at any M&+ concentration
Horse liver aldehyde dehydrogenase [1,2],like the enzymes purified from other mammalian source(s3-8), is isolated as a
Summary
From the Departmentof Biochemistry, Purdue University, West Lafayette, Indiana 47907. The molecular weight of aldehyde dehydrogenase, as determined by sedimentation equilibrium, decreased from 260,000 in the absence of M&’ to 130,000 in the presence of 0.4 nm Mg’. Assuming that the tetrameric and dimeric forms of the enzyme can function with half-of-sites and all-of-sites reactivities, respectively, we can show that anexcellent correlation exists between theapparent molecular weight and the specific activity of the enzyme at any M&+ concentration. The metalcould cause an alterationin structure such that the enzyme exhibits all-of-sitersather thanhalf-of-sites reactivity In this communication, we wiU show that alterations of molecular weight of the PI 5 horse liver enzyme occur in the presence of M$+ and will discuss how this may be related to the stimulationof catalytic activity.
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