Bell J H, Curley K, Pratt R F
Department of Chemistry, Wesleyan University, Middletown, Connecticut, 06459, USA.
Biochem Biophys Res Commun. 2000 Aug 11;274(3):732-5. doi: 10.1006/bbrc.2000.3195.
Serine beta-lactamases are inhibited by phosphonate monoester monoanions. These compounds phosphonylate the active site serine hydroxyl group to form inert, covalent complexes. Since spontaneous hydrolysis of these phosphonates is generally quite slow, the beta-lactamase active site must have considerable affinity for the (presumably) pentacoordinated phosphonyl transfer transition state. Structural analogs of such a transition state might well therefore be effective and novel beta-lactamase inhibitors. Complexes of vanadate with hydroxamic acids may be able to achieve such a structure. Indeed, mixtures of these two components, but neither one alone, were found to inhibit a typical class C beta-lactamase. A Job plot of the inhibition by vanadate/benzohydroxamic acid mixtures indicated that the inhibitor was a 1:1 complex for which an inhibition constant of 4.2 microM could be calculated. A bacterial DD-peptidase, structurally similar to the beta-lactamase, was also inhibited (K(i) = 22 microM) by this complex. A similar rationale would suggest that other serine hydrolases might also be inhibited by these mixtures. In fact, chymotrypsin was inhibited by a complex of vanadate with benzohydroxamic acid (K(i) = 10 microM) and elastase by a complex with acetohydroxamic acid (K(i) = 90 microM).
丝氨酸β-内酰胺酶受膦酸单酯单阴离子抑制。这些化合物使活性位点丝氨酸羟基膦酰化，形成惰性共价复合物。由于这些膦酸酯的自发水解通常相当缓慢，β-内酰胺酶活性位点必定对（大概）五配位膦酰转移过渡态具有相当高的亲和力。因此，这种过渡态的结构类似物很可能是有效的新型β-内酰胺酶抑制剂。钒酸盐与异羟肟酸的复合物或许能够形成这样的结构。实际上，发现这两种成分的混合物（而非单独的任何一种成分）能够抑制一种典型的C类β-内酰胺酶。钒酸盐/苯甲酰异羟肟酸混合物抑制作用的Job曲线表明，抑制剂是一种1:1复合物，其抑制常数为4.2微摩尔。一种结构与β-内酰胺酶相似的细菌DD-肽酶也被这种复合物抑制（抑制常数K(i)=22微摩尔）。类似的原理表明，其他丝氨酸水解酶或许也会被这些混合物抑制。事实上，胰凝乳蛋白酶被钒酸盐与苯甲酰异羟肟酸的复合物抑制（抑制常数K(i)=10微摩尔），弹性蛋白酶被与乙酰异羟肟酸的复合物抑制（抑制常数K(i)=90微摩尔）。
