The inhibition of brain hexokinase by adenosinediphosphate and sulfhydryl reagents
Sols, A.; Crane, R.K.
Journal of Biological Chemistry 206(2): 925-936
1954
ISSN/ISBN: 0021-9258 PMID: 13143054 Accession: 025832814
Brain hexokinase prepns. apparently require free sulfhydryl groups for activity as indicated by cysteine-reversible p-chloromercuribenzoate inhibition and o-iodosobenzoate inactivation. The 50-fold purified prepn. is completely inhibited by about 10 moles of p-chloromercuribenzoate per 100,000 g. of protein. The enzyme is sensitive to heavy metals and protected by metal-binding agents. Addition of glycerol to the concentrated purified prepns. of the particulate enzyme improves their stability on storage. Activity is max. in the range pH 6 to 8. The Q10[degree] are from 0.10[degree], 3.5; 10-20[degree], 2.8; 20-30[degree], 2.3; 30-40[degree], 2.2. Heating at 55[degree] inactivates the enzyme within 15 min. A half maximal rate is obtained at 8 x 10-4 [image] Mg++. When Mg++ is not limiting, the half max. rate occurs at 1.3 x 10-4 [image].ATP. ADP inhibits the enzyme competitively with ATP. The enzyme has the same apparent affinity for both nucleotides. Neither AMP nor pyrophosphate affects enzyme activity.