Genetic Variation for Enzyme Structure and Systemic Regulation in Two New Haplotypes of the @ - Glucuronidase Gene of Mus musculus

Two new haplotypes of the [Gus] gene complex have been characterized following their transfer from Mw, musculw, castmeus, where they were found, to a C57BL/6J genetic background. The [GUSJCs haplotype carries a new structural allele, Gus-sea, coding for enzyme with decreased thermolability and lacking an antigenic site present in other ~-glucuronida~ allozymes. The [GuslCL haplotype carries another new structural allele, Gus-&, that codes for enzyme with increased thermolability and possessing the antigenic site. Both CS and CL @-glucuronidase have the same catalytic activity/molecule as the standard B allozyme from C57BL/6J mice. Mice carrying either the [Gus]“ or [GusfCL haplotype have reduced enzyme activity in all tissues examined at all stages of development. The reduced enzyme activity is partially accounted for by reduced rates of enzyme synthesis, and the remainder probably results from increased rates of enzyme turnover. 8-Glucuronidase mRNA levels in these mice were not reduced suggesting that the observed reduction in enzyme synthesis is due to a decreased efficiency of translation for CS and CL mRNA.