XXXX dehydrogenase from @entity14921 : ligand-induced conformational changes.

@entity2125 @entity573 @entity1133 @entity377 @entity1110 @entity14921 @entity3776
@entity3776 dehydrogenase from @entity14921 is inactivated by trypsin, chymotrypsin, pronase E, thermolysin, 4.0 M @entity1133 , and by heating to 49 degrees C. It is protected, to varying degrees, against all these forms of inactivation by @entity3776 , @entity2125 +, and @entity1110 +. When these ligands are present at 10 times their respective @entity573 concentrations, protection by @entity2125 + or @entity3776 is substantially greater than protection by @entity1110 +. A detailed analysis was undertaken of the protective effects of these ligands, at varying concentrations, on proteolysis of @entity3776 dehydrogenase by thermolysin. This study confirmed the above conclusion and permitted calculation of @entity573 values for @entity2125 +, @entity1110 +, and @entity3776 that agree with such values determined by independent means. For @entity1110 +, two @entity573 values, 6.1 microM and 8.0 mM, can be derived, associated with protection against thermolysin by low and high @entity1110 + concentrations, respectively. The former value is in agreement with other determinations of @entity573 and the latter value appears to represent binding of @entity1110 + to a second site which causes inhibition of catalysis. A Ki value of 10.5 mM for @entity1110 + was derived from inhibition studies. The principal conclusion from these studies is that @entity2125 + binding to @entity14921 @entity3776 dehydrogenase results in a larger global conformational change of the enzyme than does @entity1110 + binding. Presumably, a substantially larger proportion of the free energy of binding of @entity2125 +, compared to @entity1110 +, is used to alter the enzyme's conformation, as reflected in a much higher @entity573 value. This may play an important role in enabling this dual @entity377 -specific dehydrogenase to accommodate either @entity2125 + or @entity1110 + at the same binding site.
