Glutamine Requirement for the Inosinic Acid Transformylase Reaction

Thetin–homocysteine transmethylase. Some further characteristics of the enzyme from rat liver

“…Sodium mercaptoacetate, however, acted as an inhibitor, and at a concentration of 0-03M caused a reduction in initial reaction rate of 26%. An inhibition of the thetin-homocysteine transmethylase of pigeon liver by mercaptoacetate has been reported by Sloane et al (1956), who found that the effect of this compound could be overcome by the addition of excess of the substrates, suggesting that the inhibition was competitive. Sodium sulphide (0-03M) had no inhibitory effects on the rat-liver enzyme.…”

“…Some properties of the thetin-homocysteine transmethylase from pigeon liver, including its inhibition by mercaptoacetate (thioglycollate), have been briefly reported by Sloane, Boggiano, Coulomb & Hutchings (1956), and Durell & Anderson (1956) have described the characteristics of the enzyme from horse liver. In these studies enzymic activity was followed by colorimetric determination of the methionine formed.…”

Folic Acid Coenzymes and One‐Carbon Metabolism

“…will replace I M P as the formyl donor in reaction (18). In crude enzyme preparations, the requirement for GAR in reaction (18) may be satisfied by the addition of glycine, ATP and glutamine (253,255). If hFH4 dehydrogenase and serine hydroxymethylase (see Sections IVC and 1V.D) are present, the formation of AICAR from IMP may also be combined with the biosynthesis of serine (242,253) according to the equation :…”