Hypoxanthine-guanine phosphoribosyltransferase deficiency: activity in normal, mutant, and heterozygote-cultured human skin fibroblasts.

Cultured skin fibroblasts from patients deficient for the enzyme hypoxanthine-guanine phosphoribosyltransferase (PRT) activity show very low but nevertheless significant levels of apparent PRT enzyme despite absence of detectable activity (<0.004% of normal) in erythrocytes of the same patients. In fibroblasts this mutant enzyme is more heat labile than the normal enzyme. These findings indicate that PRT deficiency in this disorder is not due to a deletion mutation of the PRT locus.Individual cultured skin fibroblasts from heterozygote females for PRT deficiency show normal, intermediate, or very low levels of PRT activity. The mosaicism demonstrated in the heterozygotes for this X-linked disorder accounts for the cells with normal and very low activities of PRT. Intermediate activity can best be explained by the phenomenon of metabolic cooperation presumably from the transfer of either PRT enzyme or messenger RNA, from normal to mutant cells.