Isozymes of rodent 5‘‐nucleotidase: evidence for two independent structural loci Umph‐1 and Umph‐2

Abstract

Two distinct isozymes (UMPH-1 and UMPH-2) which hydrolyse pyrimidine 5'-nucleotides have been identified in mouse, rat and Chinese hamster tissues. One of these, UMPH-1 appears to be specific for pyrimidine 5'-nucleotides, whereas the other, UMPH-2 has a broader substrate specificity. UMPH-1 and UMPH-2 show differences in their expression in different tissues. The evidence suggests that UMPH-1 and UMPH-2 are coded by distinct structural gene loci, Umph-1 and Umph-2. These isozymes have not been identified in man, and it is suggested that they may have overlapping electrophoretic mobility.

5'-Nucleotidases, Nucleosides and their Distribution in the Brain: Pathological and Therapeutic Implications

“…Cytosolic 5'-nucleotidase III is widely expressed in mouse, rat and human tissues [98,145,146], is Mg 2+ dependent [147], functions as a monomer (the molecular mass is 34 kDa) [98,148], and hydrolyzes pyrimidine monophosphates [147]. However, cN-III shows the highest affinity for Cyd monophosphate (CMP) (K m 10-150 M) [81,91,147].…”

“…Genetic mutations (deficiencies) of cN-III in reticulocytes cause hemolytic anemia [147,148]. Cytosolic 5'(3')-deoxyribonucleotidase (cdN, PN-II, dNT-1, UMPH-2) is widely distributed in human, mouse and rat tissues [99,145,[149][150][151]. Its gene has been localized on chromosome 17q25 [151].…”

Pyrimidine 5′‐nucleotidase activity in normal and deficient human lymphoblastoid cells

“…This was carried out as described previously (Swallow et al, 1983a) except that the voltage was increased to 5.2 V/cm.…”

“…There are at least two distinct pyrimidine 5'-nucleotidases in mammalian tissues (Swallow et al, 1983a(Swallow et al, , 1983bPaglia et al, t984). In man one of these, UMPH1, is deficient in certain patients with haemolytic anaemia, whilst UMPH2 is unaffected (Swallow et al, 1983b;Paglia et al, 1984).…”

“…Little is known about the tissue distribution of UMPH1 except that it was reported not to occur in fibroblasts (Beutler et al, 1980), but it is likely that UMPH1 does occur in other tissues since in rodents the homologous enzyme has a wide tissue distribution (Swallow et al, 1983a). Furthermore, in man a pyrimidine nucleotidase of mobility comparable with UMPH 1 and UMPH2 is seen in most tissues (Swallow et al, 1983a) but because these two isozymes have a very similar electrophoretic mobility it is not entirely clear whether one or both are present in any particular tissue. We have examined lymphoblastoid cell lines from pyrimidine nucleotidasedeficient patients, obligatory heterozygotes and control individuals in order to assess firstly, whether UMPH1 and the deficiency of UMPH1 can be detected in these cells, and secondly whether any derangement of pyrimidine metabolism consequent upon this defect can be demonstrated.…”