COMPLETE SEQUENCE OF GLYCOLYTIC-ENZYMES IN THE MYCORRHIZAL BASIDIOMYCETE, SUILLUS-BOVINUS

Axenic cultures of Suillus bovinus were cultivated in inorganic liquid medium with glucose as a carbon source at 25 degrees C and continuous supply of oxygen by aeration with compressed air in the dark. Exogeno us fructose as sole carbon source yielded about 50% less increase in d ry weight than glucose. This resulted from different uptake velocities . Sucrose as sole exogenous carbon source yielded no measurable increa se in dry weight. In glucose cultures, activities of all glycolytic en zymes were found. Maximum specific activities varied largely (from abo ut 60 [fructose 6-phosphate kinase] to about 20 000 [triosephosphate i somerase] nmoles.mg protein(-1).min(-1)). Apparent K-m-values also var ied over more than two orders of magnitude (0.035 mM [pyruvate kinase] to 6.16 mM [triosephosphate isomerase]). Fructose 6-phosphate kinase proved to be the fructose 2,6-bisphosphate-regulated type, aldolase th e divalent cation-dependent (class II) type and glyceratephosphate mut ase the glycerate 2,3-phosphate-independent type of the respective enz ymes. Eight of the 10 enzymes exhibited pH-optima between 7.5-8.0. Tri osephosphate isomerase and pyruvate kinase showed highest activities a t pH 6.5. Regulatory sites within the glycolytic pathway of Suillus bo vinus are discussed, fructose 6-phosphate kinase appears to be its mai n bottle neck.