Purification and characterization of phosphohexose isomerase from human gastrointestinal carcinoma and its potential relationship to neuroleukin.
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.
Baumann
M
M
Institute of Biochemistry, Medical Faculty, University of Erlangen-Nuremberg, Federal Republic of Germany.
Brand
K
K
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
D006133:Growth Substances; D008222:Lymphokines; D005956:Glucose-6-Phosphate Isomerase