Immobilization of Kluyvera citrophila penicillins acylase on controlledpore ceramics.

Penicillin acylase was purified from Kluyvera citrophila and immobilized on glutaraldehyde derivatives of silanized controlled-pore ceramics. The behaviour of the enzyme attached to TiO2, Al2O3 and SiO2 in the hydrolytic reaction are compared with that of the native enzyme as well as of the enzyme bound to CNBr-activated Sepharose 4B. The enzyme immobilized on TiO2 shows an efficiency of about 95% on the basis of protein bound. The penicillin acylase attached to SiO2, unlike the enzyme immobilized on TiO2, Al2O3 and Sepharose looses activity markedly in every cycle of use.

Bacterial citrate lyase.

Bacterial citrate lyase, the key enzyme in fermentation of citrate, has interesting structural features. The enzyme is a complex assembled from three non-identical subunits, two having distinct enzymatic activities and one functioning as an acyl-carrier protein. Bacterial citrate lyase, si-citrate synthase and ATP-citrate lyase have similar stereospecificities and show cofactor cross-reactions. On account of these common features, the citrate enzymes are promising markers in the study of evolutionary biology. The occurrence, function, regulation and structure of bacterial citrate lyase are reviewed in this article.