Genetics of insect hemolymph beta-N-acetylglucosaminidase in the silkworm, Bombyx mori.

The distribution of insect hemolymph beta-N-acetylglucosaminidase was investigated in the silkworm, Bombyx mori. Activity in 115 varieties was 6.92 +/- 3.22 units/ml, ranging from 1.4 to 17.0 units/ml. No enzyme-deficient individuals were observed. By selecting individuals showing either high or low enzyme activities, homozygotes were separated with activities varying 10-fold between isolates. No differences in activity of alpha-mannosidase and beta-galactosidase were observed. Thus, it appears that high- or low-enzyme silkworms (High or Low lines) shared the same genetic background except for the gene concerning the activity of beta-N-acetylglucosaminidase. Studies on the heredity of the enzyme indicated that the synthesis of the enzyme protein was controlled by an autosomal allele. Examination by immunotitration and CM52-cellulose column chromatography revealed that the difference in activity between High and Low lines was due to the amount of the active enzyme, but not to an endogeneous activator or inhibitor. Furthermore, there was no isozymic difference in beta-N-acetylglucosaminidase. Slab gel electrophoresis on polyacrylamide showed a species of enzyme (A) that stained more intensely in the High line. For the second species of enzyme (B), the converse was true. This evidence suggests that enzyme levels in hemolymph are under the control of a gene affording association of enzyme subunits to the active enzyme molecule.