Glycine and glyoxylate decarboxylation in Nicotiana rustica roots

Glycine was decarboxylated only by intact mitochondria to yield carbon dioxide, formaldehyde, and ammonia, probably present as pyridoxamine phosphate. The formaldehyde could become incorporated into serine, via N⁵N¹⁰ methylene-FH₄, and a requirement was demonstrated for pyridoxal phosphate. Similarly, glyoxylate with pyridoxamine phosphate was also decarboxylated to formaldehyde and carbon dioxide. Glyoxylate could be decarboxylated by at least two additional pathways. One consisted of oxidative decarboxylation yielding formate and carbon dioxide, and requiring thiamine pyrophosphate, manganese ions, and oxygen. The other consisted of glyoxylate condensation with 2-oxoglutarate, yielding carbon dioxide and an intermediate which, upon decarboxylation, appeared to be hydroxylevulinic acid.