Evaluation of the Protein Components of Citrate Lyase from Klebsiella aerogenes

Abstract

1 The specific activity of homogeneous and fully active citrate lyase from Klebsiella aerogenes was found to be 55 U per mg protein. This corresponds to about 1.8 nmol enzyme (Mr∼ 550000). 2 Based on these data and by use of several different methods it was found that about 4-5 mol acyl carrier protein are present in the lyase. 3 Evidence is presented which excludes the participation of the cysteine residue, present in the acyl carrier protein, as an acyl-carrying group. Thus, as in fatty acid synthetase, only the cysteamine residue of this subunit carries the acyl groups. 4 the composition of citrate lyase from three different proteins was confirmed. The molecular weights of these subunits are about 10000, 32000 and 54000; the latter molecular weight, which was questionable, was found to be 56000 by ultracentrifugation studies of the isolated, homogeneous protein. 5 The molar ratio of the three subunits mentioned in paragraph 4 was found to be about 1:1:0.8. This ratio indicates the presence of six copies of each of the three different subunits in the native enzyme complex, which probably consists of a hexamer.