On the detection of functional and structural enzyme mutants by coordinated affinity chromatography and isoelectric focusing

A method of studying structural and functional heterogeneity of enzymes has been developed and tested on chymotrypsin. The enzyme, prepared from single mouse pancreata, has been fractionated with respect to function and charge content by a combination of affinity chromatography and isoelectric focusing. By comparing chymotrypsin isolated from isogenic strains, chymotrypsinogen of strains A/Sn and NZB was found to be genetically heterogeneous, thus not revealed as different chymotrypsin forms of a single zymogen. Chymotrypsinogen originating from two loci was investigated, and structural and functional differences of the corresponding enzymes were determined. At both loci, structural allelomorphism was indicated. At one locus, the structural heterogeneity was also found to be reflected in functional heterogeneity of the corresponding enzymes. By mating the two strains and fractionating the enzyme of the cross, the differences were shown to be inherited.