STUDIES ON ALKALINE PHOSPHATASE - INHIBITION BY PHOSPHATE DERIVATIVES AND SUBSTRATE SPECIFICITY
STUDIES ON ALKALINE PHOSPHATASE - INHIBITION BY PHOSPHATE DERIVATIVES AND SUBSTRATE SPECIFICITY
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DOI：
10.1042/bj1041011
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发表时间：
1967-01-01
影响因子：
4.1
通讯作者：
WALKER, PG
中科院分区：
文献类型：
--
作者：
FERNLEY, HN;WALKER, PG
1. The kinetics of inhibition of calf-intestinal alkaline phosphatase by inorganic phosphate, fluorophosphate, inorganic pyrophosphate, β-glycerophosphate and adenosine 5′-triphosphate in the range pH8–10 were investigated. The reference substrate was 4-methylumbelliferyl phosphate. 2. The inhibitions were `mixed' in that both Km and V were affected, but the competitive element was by far the stronger. 3. In each case the pH profile for the competitive Ki was similar to the pH profile for Km. Since the Km and Ki values both change 100-fold over the pH range 8–10, it is concluded that the inhibitors compete with the substrate for the same active site. 4. It was also found that the enzyme preparation hydrolysed fluorophosphate, pyrophosphate and adenosine 5′-triphosphate as readily as it hydrolysed 4-methylumbelliferyl phosphate and β-glycerophosphate. Each pH–activity curve, however, had a different shape, but with the exception of pyrophosphate the activity approached the same maximum value at high pH. 5. Attempts to separate the phosphomonoesterase and pyrophosphatase activities by column chromatography were not successful, and the results of other experiments listed suggest that the two activities are a property of the same enzyme. 6. The effect of Mg2+ ions is briefly mentioned: the phosphomonoesterase activity is enhanced whereas the pyrophosphatase and adenosine triphosphatase activities are strongly inhibited in the presence of excess of Mg2+ ions.
