Comparative kinetics and inhibition of a carbonic anhydrase from Chlamydomonas reinhardii.

A native carbonic anhydrase (CA) from Chlamydomonas reinhardii exhibited an apparent molecular weight of 165,000. Denaturation under reducing conditions yielded a single polypeptide, mol. wt 42,000, while the same treatment under nonreducing conditions yielded higher molecular weight aggregates at least two of which could be reactivated to exhibit enzyme activity. In CO2 hydration the enzyme has a Km value of 3.4 mM and a relatively high turnover number. It is very sensitive to inhibition by sulfonamide and moderately sensitive to anion inhibition. In general, the C. reinhardii enzyme resembles many higher plant CAs in its existence as an oligomer. However, it is more like the CAs from animal species in its catalytic versatility and sensitivity to sulfonamides.