Disposal of Surplus One-Carbon Fragments

Two reactions are of special interest thymidylate synthetase (Section 10.3.3) and remethylation of homocysteine to methionine (Section 10.3.4). This latter reaction is central to the control of the metabolism of one-carbon compounds and folate. 

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Disposal of Surplus One-Carbon Fragments With the exception of serine hydroxymethyltransferase (Secdon 10.3.1.1), aU of the reactions shown in Figure 10.4 as sources of one-carbon subsdtuted folates are essentially catabolic reactions. When there is a greater entry of single carbon units into the folate pool than is required for biosynthetic reactions, the surplus can be oxidized to carbon dioxide byway of 10-formyl-tetrahydrofolate, thus ensuring the avaUabUity of tetrahydrofolate for catabolic reactions. 

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