Post-translational modification of enzymes: processing genes.

Much of the total genomic variation in eukaryotic organisms may be due to genes other than those coding the primary translation product. Allelic variation, especially as detectable by electrophoresis, in the post-translational processing of enzymes has been briefly reviewed with considerable attention given to a mouse gene (Neu-1) and its pleiotropic effects on several lysosomal hydrolases. Liver acid phosphatase, alpha-mannosidase, arylsulfatase B, and alpha-glucosidase are differentially sialylated as the result of allelic variation for a gene controlling liver neuraminidase activity. Strain SM/J has only 15-20% of the total neuraminidase activity of control strains and is almost totally deficient in the more heat labile of two components of liver activity. The locus controlling this variation (Neu-1) maps very near the D end of H-2 on chromosome 17, apparently within the S region of H-2. A homologous gene has been mapped near the MHC of the rat. The exact nature of the mouse mutant and its relationship to several human diseases characterized by neuraminidase deficiency has not been determined.