One - carbon unit production in P . carbinolicus . One-carbon units carried by tetrahydrofolate (THF) derive from serine, producing glycine. In the absence of the glycine cleavage complex, excess glycine might be deaminated to glyoxalate by aminotransferases using pyridoxal-5′-phosphate (PLPO). Fusion of two glyoxalate molecules by glyoxalate carboligase, rearrangement to hydroxypyruvate with the aid of glutathione (GT), and amination would regenerate serine. An alternative pathway involving phosphorylation allows hydroxypyruvate to enter glycolysis to be catabolized.