Effect of p-chloromercurybenzoate on the MDH-activity of cytosol and rat liver submitochondrial fractions in different buffers.
The effect of p-chloromercurybenzoate (p-CMB) on the MDH-activity of cytosol and submitochondrial fractions (matrix and inner membranes) of rat liver is studied in different buffer systems with identical pH. It is found that p-CMB has two effects on the MDH-activity, depending on the subcellular localization of the enzyme and on the type of buffer used: inhibitory (for the enzyme of the three fractions in HEPES-NaOH and potassium-phosphate buffers) and activating (for the enzyme of the submitochondrial fractions in Tris-HCI buffer). The effect of the SH-reagent on the formation and stability of enzyme-substrate complexes in the different buffers is also studied, as well as the temperature dependence of the p-CMB action on the MDH-activity of the preparations. It is found that the association of m-MDH with the inner mitochondrial membranes does not change its kinetic behaviour. The probable different conformation of the mitochondrial enzyme in the different buffer systems is discussed.
D000818:Animals; D002021:Buffers; D002729:Chloromercuribenzoates / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D009243:NAD / Q000378:metabolism; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology; D013696:Temperature; D013997:Time Factors
D002021:Buffers; D002729:Chloromercuribenzoates; D009243:NAD; D008291:Malate Dehydrogenase