title: Purification and characterization of phosphohexose isomerase from human gastrointestinal carcinoma and its potential relationship to neuroleukin.
abstract: Phosphohexose isomerase (PHI) derived from human gastrointestinal tumor tissue was isolated by specific elution from a cation exchanger. The identity of three PHI variants in the purified preparation could be demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing analysis. By preparative IEF the variants could be resolved to high homogeneity. The monomer of the common major variant with a pI of 9.1 revealed a molecular weight of 60,000, whereas for the cancer-associated variants with a pI of 8.9 and 8.6, a molecular weight of 57,000 and 56,000, respectively, was determined. The results obtained support the hypothesis that those variants are due to a specific intracellular cleavage of the enzyme in the malignant cells. Since it has been shown that the Mr 56,000 protein neuroleukin exhibits a strikingly high degree of homology with PHI (M. Chaput et al., Nature (Lond.), 332: 454-455, 1988; P. Faik et al., Nature (Lond.), 332: 455-456, 1988), the described specific cleavage of PHI might be responsible for the conversion of an enzyme to a trophic factor.
authors.affiliation: Institute of Biochemistry, Medical Faculty, University of Erlangen-Nuremberg, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Baumann
authors.forename: K
authors.initials: K
authors.lastname: Brand
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D005770:Gastrointestinal Neoplasms / Q000201:enzymology*; D005956:Glucose-6-Phosphate Isomerase / Q000302:isolation & purification*; D006133:Growth Substances / Q000032:analysis*; D006801:Humans; D007525:Isoelectric Focusing; D008222:Lymphokines / Q000032:analysis*; D008970:Molecular Weight
chemical_list: D006133:Growth Substances; D008222:Lymphokines; D005956:Glucose-6-Phosphate Isomerase