Interaction of bovine carbonic anhydrase with acetate ions

Amos Lanir*, Gil Navon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The binding of acetate ions to bovine carbonic anhydrase (carbonate hydrolyase, EC 4.2.1.1) was investigated by NMR and by inhibition measurements. Two acetate ions were found to interact with the protein but only one is linked with the inhibition of the esterase activity of the enzyme. The NMR spectrum of the anion is sensitive to the stronger acetate binding, which is to a noninhibitory binding site. This acetate ion could be titrated with monovalent anions as N3- but not with p-toluenesulfonamide. The noninhibitory acetate ion performs an isotropic random motion faster than that of the enzyme. The correlation time for the tumbling of the methyl group was calculated from the T1/T2 ratio, as well as from the NMR line-broadening ratio at two NMR frequencies and was found to be (2.3·10-9 0.8)·10-9 s. The binding of the two ligands decreases with pH and is probably dependent upon two different groups on the enzyme with pKa values of 7.5 and 7.4 for the binding of the inhibitory and noninhibitory acetate ions, respectively.

Original languageEnglish
Pages (from-to)65-74
Number of pages10
JournalBBA - Enzymology
Volume341
Issue number1
DOIs
StatePublished - 21 Mar 1974

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