Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
 2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Due to the lack of de novo purine nucleotide biosynthesis, hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) is an essential enzyme in the human parasite Schistosoma mansoni for supplying guanine nucleotides and has been proposed as a potential target for antiparasitic chemotherapy. While the enzyme can be purified from adult schistosome worms, yields are too low to allow extensive structural and kinetic studies. We therefore cloned and sequenced the cDNA and gene encoding the schistosomal enzyme but were unable to positively identify the amino-terminal sequence of the enzyme from the DNA sequence. Knowledge of the exact amino terminus was necessary before accurate expression of active enzyme could be attempted. Therefore, we purified the HGPRTase from crude extracts of the adult worms. The purified enzyme has a subunit molecular mass of 26 kDa and an amino-terminal sequence of Met-Ser-Ser-Asn-Met. This sequence matched one of the potential initiation sites predicted from the cDNA and gene sequence. We next expressed the correct size cDNA of the S. mansoni HGPRTase in Escherichia coli using a vector that is regulated by a bacterial alkaline phosphatase promoter and uses an E. coli signal peptide for secretion of expressed product into the periplasmic space. Using this expression system, some of the recombinant enzyme is secreted and found to have a correct amino terminus. That remaining in the cytoplasm has part of the signal peptide attached to the amino terminus. The recombinant schistosomal HGPRTase isolated from the periplasm of the transformed E. coli was purified and found to have kinetic and physical properties identical to those of the native enzyme.
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PMID:The hypoxanthine-guanine phosphoribosyltransferase of Schistosoma mansoni. Further characterization and gene expression in Escherichia coli. 219 39

We describe the isolation and characterization of tryptic peptides of human erythrocyte hypoxanthine-guanine phosphoribosyltransferase. The digest was separated by reverse-phase high pressure liquid chromatography into 30 peaks, 26 of which contained purified peptides. The four complex peaks were resolved by high pressure liquid chromatography with a different reverse-phase column. Each peptide predicted from the recently described amino acid sequence of human erythrocyte hypoxanthine-guanine phosphoribosyltransferase was isolated from this peptide map. Sequence analysis of the purified peptides identified two peptides, 14 and 14d, that differed by an Asn/Asp heterogeneity at the position corresponding to residue 106 of the intact protein. Additional studies indicate that this heterogeneity is due to deamidation of the protein in vivo. This post-translational modification appears to be responsible for some of the electrophoretic heterogeneity observed in the normal erythrocyte enzyme.
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PMID:Human hypoxanthine-guanine phosphoribosyltransferase. Tryptic peptides and post-translational modification of the erythrocyte enzyme. 717 69