CLONING OF MOUSE GAMMA-GLUTAMYL HYDROLASE IN THE FORM OF 2 CDNA VARIANTS WITH DIFFERENT 5' ENDS AND ENCODING ALTERNATE LEADER PEPTIDE SEQUENCES

Mouse-liver gamma-glutamyl hydrolase (GH) is a lysosomal endopeptidase with an acid pH optimum that is activated by sulfhydryl compounds and preferentially hydrolyzes the most proximal gamma-glutamyl linkage of longer chain polyglutamates of folates and their analogues. We descri be the cloning of this mouse lysosomal cDNA enzyme from liver GK mRNA in the form of two cDNA variants (1.295 and 1.268 kb in length) differ ing 14-fold (Variant I versus Variant II) in relative frequency that e xhibited 5'-end heterogeneity and encoded alternate leader peptides. T he 5' UTR in these variants also differs in length by 27 nucleotides. Otherwise, the ORF and 3' UTR in each case are the same. These cDNAs e ncode a protein in which the deduced amino acid sequence shares 78.9 a nd 69.1% identity to rat and human GH sequences, respectively. Amino a cid sequence comparisons among the three species identified three cons erved Asn sites and two conserved Cys residues that may be sites of gl ycosylation and sulfhydryl compound activation, respectively Variant I GH mRNA was more abundant than Variant II GH mRNA in all mouse tissue s examined. Variant I GH mRNA levels were extremely high in salivary g land, moderately high in kidney, liver, lung, stomach and uterus, low in small intestine, brain and fetal liver and relatively rare in thymu s, spleen and skeletal muscle. Abundance of GH mRNA among tumors varie d from low to high, with no discernible correlation with their tissue of origin. (C) 1998 Elsevier Science B.V. All rights reserved.