CHARACTERIZATION OF SOME GLYCOLYTIC-ENZYMES FROM HUMAN RETINA AND RETINOBLASTOMA

  • 1 January 1982
    • journal article
    • research article
    • Vol. 42  (10) , 4228-4232
Abstract
Glycolytic enzymes were studied from normal human retinas (fetal and adult) and from retinoblastomas of 8 patients and an established retinoblastoma cell line. No significant differences were found in enzyme activities in the tissues investigated except for hexokinase and pyruvate kinase, which were significantly decreased in the tumor cells. In fetal retina 5 different forms of pyruvate kinase could be detected by electrophoresis (K4, K3M, K2M2, KM3 and M4). In adult retina the K4 isozyme was almost absent; in retinoblastoma the M4 isozyme was hardly present. In the retinoblastoma cell line the M4 isozyme was completely absent. Alanine inhibition of pyruvate kinase was in agreement with the electrophoretic pattern. Pyruvate kinase from the retinoblastoma cell line was more inhibited than the pyruvate kinase of fetal retina and retinoblastoma and was even more inhibited than adult retina. Electrophoresis of aldolase from adult retina revealed the presence of all potential A-C hybrids (A4, A3C, A2C2, AC3 and C4). Fetal retina is characterized by the predominance of the A type. The same patterns were observed in the retinoblastoma cell line and retinoblastoma, but in other brain tumors e.g., gliomas of adults, a 5-membered A-C hybrid set was found. Electrophoresis of hexokinase from normal fetal and adult retina revealed the predominance of hexokinase type 1; retinoblastoma and retinoblastoma cell line are characterized by considerable amounts of hexokinase type II. The isozyme shifts in retinoblastoma result in an enzyme pattern identical to that of fetal retina except for the presence of hexokinase type II.