Citrate lyase: molecular weight and subunit structure

Abstract

The purification of citrate lyase (citrate oxalacetate-lyase, EC 4.1.3.6) from Aerobacter aerogenes was described earlier by one of us (SivaRaman, 1961). In the present communication, the molecular weight of 314,000 reported by Bowen and Rogers (1963) has been shown to be inconsistent with the gel filtration behavior of the enzyme and a considerably higher value of 575,000 has been obtained on redetermination by the Archibald procedure. Data have been presented here which suggest that the enzyme is composed of eight subunits of identical size. The octameric form of the enzyme has been shown to dissociate reversibly in two stages, first to a tetramer and then to a dimer, on dialysis against EDTA solutions of low ionic strengths and pH 7.4. The enzyme molecule has also been shown to disaggregate in stages on reaction with p-chloromercuribenzoate (PCMB).