Inhibition of carbonic anhydrases I and II by N-unsubstituted carbamate esters.

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Parr JS, Khalifah RG

Inhibition of carbonic anhydrases I and II by N-unsubstituted carbamate esters.

J Biol Chem. 1992 Dec 15;267(35):25044-50.

PubMed ID

1460006 [ View in PubMed

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Abstract

We previously showed that the zinc metalloenzyme carbonic anhydrases (CA I and II isozymes) bind "neutral" amides and related compounds as anions through coordination of their deprotonated amide nitrogen to the active site zinc (Rogers, J. I., Mukherjee, J., and Khalifah, R. G. (1987) Biochemistry 26, 5672-5679). Urethan, the ethyl carbamate ester, was among such compounds. The present study was designed to test whether other N-unsubstituted carbamate esters of pharmacological interest (as sedatives, hypnotics, anxiolytics, and skeletal muscle relaxants) were capable of binding to CA in the same manner. We studied the interaction of human CA I and II with urethan, phenyl carbamate, ethinamate, meprobamate, and methocarbamol. Phenyl carbamate studies were greatly complicated by its uncatalyzed hydrolysis via an elimination mechanism to form cyanate, a powerful CA inhibitor. In general, the compounds display: 1) slow on-off inhibition binding kinetics in the seconds range, 2) maximal inhibitor affinity at alkaline pH, and 3) characteristic three-band visible spectra of their complexes with cobalt-substituted CA I. These properties are shared with the previously studied amide inhibitors and are taken as evidence that the deprotonated carbamate nitrogen coordinates to the active site metal ion. CA I appeared to bind carbamate esters more tightly than CA II, an unusual 1000-fold selectivity being seen in the case of methocarbamol. The inhibition by these drugs is not sufficiently strong to implicate CA I and II in their mechanism of action. However, it does suggest the possible existence of previously unsuspected similarities between binding to CA and to their physiological receptors or targets, particularly the involvement of zinc.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Ethinamate	Carbonic anhydrase 1	Protein	Humans	Yes	Inhibitor	Details
Ethinamate	Carbonic anhydrase 2	Protein	Humans	Yes	Inhibitor	Details
Methocarbamol	Carbonic anhydrase 1	Protein	Humans	No	Inhibitor	Details