{beta}-N-Acetylhexosaminidases of Physarum polycephalum: Some Characteristics of a New Form of the Enzyme

Department of Biochemistry, Queen Elizabeth College, University of London, Campden Hill, London W8 7AH, U.K. G. D. Searle&Co. Ltd, Research Division, Lane End Road, High Wycombe, Bucks HP12 4HL, U.K. ABSTRACT SUMMARY: During axenic growth, microplasmodia of Physarum polycephalum secreted chitinase and β- N -acetylhexosaminidase. Chitin added to the medium was depolymerized to N -acetylglucosamine, but this was not used for growth. Spent culture medium contained three enzymes with activity towards 4-methylumbelliferyl-β- N -acetylglucosaminide and these were separated by chromatography on DEAE-cellulose. In previous work β- N -acetylhexosaminidases X and Y were identified. The latter form has now been resolved to yield a new form Z. The Y form can be readily distinguished from both X and Z by its lack of activity towards N, N’ -diacetylchitobiose. Comparison of β- N -acetylhexosaminidases X and Z revealed differences in thermal stability, pH optima and K m values. 3,4-Dinitrophenyl-tetra- N -acetylchitotetraoside is hydrolysed by β- N -acetylhexosaminidase Z, but not by the X form of the enzyme. Present address: Division Of Immunochemical Genetics, Mrc Clinical Research Centre, Watford Road, Harrow, Middlesex Ha1 3Uj, U.K.