TY - JOUR
T1 - Human erythrocyte thiol methyltransferase
T2 - Radiochemical microassay and biochemical properties
AU - Weinshilboum, Richard M.
AU - Sladek, Susan
AU - Klumpp, Susanne
N1 - Funding Information:
This study was supported in part by NIH grants NS 11014 and HL 17487 and National Foundation March of Dimes Grant NF 6-202. Dr. Weinshilboum
PY - 1979/9/15
Y1 - 1979/9/15
N2 - A radiochemical microassay for the measurement of thiol methyltransferase (TMT) activity in human red blood cell (RBC) membranes has been developed. Both 2-mercaptoethanol and dithiothreitol were used as substrates for the enzyme. The pH optimum of the reaction was approximately 9.0 when glycine-NaOH was used as a buffer. The apparent Michaelis-Menten (KM) value for the methyl donor for the reaction, S-adenosyl-l-methionine, was 43 μmol/1. Human RBC TMT activity was neither activated nor inhibited by Ca2+ Mg2+, or tropolone, but the enzyme was inhibited by SKF 525A and by reagents that react with sulfhydryl groups. The mean TMT activity in blood from 289 randomly selected adult white subjects was 10.93 ± 3.22 units per mg protein (mean ± S.D.). The activity was the same in samples from men and women. The results of experiments in which TMT activity was measured in mixtures of RBC membranes with relatively "low" and relatively "high" activities provided no evidence that individual variations in the enzyme activity were due to variations in endogenous TMT activators or inhibitors.
AB - A radiochemical microassay for the measurement of thiol methyltransferase (TMT) activity in human red blood cell (RBC) membranes has been developed. Both 2-mercaptoethanol and dithiothreitol were used as substrates for the enzyme. The pH optimum of the reaction was approximately 9.0 when glycine-NaOH was used as a buffer. The apparent Michaelis-Menten (KM) value for the methyl donor for the reaction, S-adenosyl-l-methionine, was 43 μmol/1. Human RBC TMT activity was neither activated nor inhibited by Ca2+ Mg2+, or tropolone, but the enzyme was inhibited by SKF 525A and by reagents that react with sulfhydryl groups. The mean TMT activity in blood from 289 randomly selected adult white subjects was 10.93 ± 3.22 units per mg protein (mean ± S.D.). The activity was the same in samples from men and women. The results of experiments in which TMT activity was measured in mixtures of RBC membranes with relatively "low" and relatively "high" activities provided no evidence that individual variations in the enzyme activity were due to variations in endogenous TMT activators or inhibitors.
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U2 - 10.1016/0009-8981(79)90025-1
DO - 10.1016/0009-8981(79)90025-1
M3 - Article
C2 - 40715
AN - SCOPUS:0018668152
SN - 0009-8981
VL - 97
SP - 59
EP - 71
JO - Clinica Chimica Acta
JF - Clinica Chimica Acta
IS - 1
ER -