Serine Transhydroxymethylase

Serine transhydroxymethylase was shown to catalyze the synthesis of l-serine from glycine and formaldehyde in the absence of tetrahydrofolate. Initial velocity, product inhibition, and exchange reaction studies showed that the addition of substrates was ordered, with glycine adding first. The effect of tetrahydrofolate on increasing the rate of serine synthesis was correlated with the effect of this coenzyme on the exchange of the α-hydrogen of glycine with protons of the solvent. The data were interpreted to mean that formaldehyde is transferred from serine to 5,10-methylene tetrahydrofolate through an intermediate enzyme-formaldehyde complex.