Abstract
Sarcoma 180 cells contain a highly specific guanylate kinase (ATP-GMP phosphotransferase, EC 2.7.4.8) that converts GMP to GDP. This tumor enzyme closely resembles in its kinetic parameters and molecular size the guanylate kinase of hog brain. With both enzymes the analogue nucleotide 6-thioguanosine 5'-phosphate behaves as a potent inhibitor, competitive with GMP, with an inhibition constant (Ki) of about 6 x 10-5 M. When examined with large amounts of hog brain enzyme, 6-thioguanosine 5'-phosphate behaves as an alternative substrate with a very low maximum velocity that is less than 0.04% of the reaction rate attainable with GMP as the substrate. The possible role of these findings in the cytolytic action of 6-thioguanine is discussed.
- Copyright ©, 1969, by Academic Press Inc.
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|