The Thermal Inactivation of Acetoacetate Decarboxylase
1970; Elsevier BV; Volume: 245; Issue: 20 Linguagem: Inglês
10.1016/s0021-9258(18)62744-9
ISSN1083-351X
AutoresAnne P. Autor, Irwin Fridovich,
Tópico(s)Biochemical Acid Research Studies
ResumoAbstract The acetoacetate decarboxylase obtained from Clostridium acetobutylicum undergoes a biphasic thermal inactivation; the rapid phase of which was temperature sensitive, whereas the slow phase was much less so. ΔHa for the rapid phase of inactivation was 49 kcal per mole. The fraction of the total activity which was lost by the rapid process was increased with increasing temperature. Acetylacetone protected the enzyme against thermal inactivation and was more effective in preventing the rapid phase than in preventing the slow phase of activity loss. When the enzyme was heated until the rapid phase was over and then chilled; subsequent reheating did not result in the reappearance of a rapid phase of inactivation. When the organism was cultured in the presence of benzoylacetone it generated an active decarboxylase which differed from the normal enzyme in several respects. This modified enzyme did not possess any latent activity; was more susceptible to thermal inactivation and exhibited a ΔHa for the rapid phase of thermal inactivation of 104 kcal per mole. A mechanism is proposed to account for the properties of the thermal inactivation of acetoacetic decarboxylase.
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