The multiple forms and kinetic properties of the N-acetyl-beta-D-hexosaminidases from colonic tumours and mucosa of rats treated with 1,2-dimethylhydrazine.

The separation and purification of the N-acetyl-beta-D-hexosaminidase activities from tumours induced by 1,2-dimethylhydrazine in the rat colon and from colonic mucosa of tumour-bearing animals are reported. Mucosa contained N-acetylhexosaminidases A and B, as well as a third form whose properties with regard to electrophoretic mobility and thermostability lay between those of A and B. Tumours contained only N-acetylhexosaminidase A and B activities. Each form possessed both N-acetylglucosaminidase (EC 3.2.1.30) and N-acetylgalactosaminidase (EC 3.2.1.53) activities, which could not be separated by a variety of techniques. The alteration of the ratio of the two specific activities in each form during purification, together with differences in the kinetic inhibition constants and behaviour during inactivation by various reagents or a temperature of 50 degrees C, supported the belief that each form contains the two enzyme activities, glucosaminidase and galactosaminidase, at separate active sites. This model is in contrast with that reported for these activities from a number of other sources. A variety of treatments reported to cause the conversion of form A into a form resembling B failed to produce such an effect on the rat colonic hexosaminidases.