Genetic variation in the purine nucleoside phosphorylase activity of sheep red cells.

Summary The purine nucleoside phosphorylase (NP) activity of sheep red cells was determined by starch gel electrophoresis and by a spectrophotometric assay technique. Some sheep had high activity (NP-high type) and some had low or zero activity (NP-low type). The enzyme deficiency is apparently confined to the red cell since other tissues from NP-low type animals had activities similar to those from NP-high type individuals. Family data indicated that NP activity is controlled by a pair of autosomal allelic genes, designated NPH and NPL. Sheep heterozygous for the NP genes had lower enzymic activities than homozygous high-type individuals. The frequency of NP types in different breeds of sheep was determined. Barbary and Mouflon sheep had activities similar to NP-high type domestic sheep; goats had high enzyme activities but their NP had a slower electrophoretic mobility than that of sheep.