Use of creatine as a dietary supplement

Decarboxylation of ornithine to putrescine by ornithine decarboxylase serves as a source of the polyamines spermidine and spermine. Ornithinemia results from deficiency of ornithine aminotransferase or ornithine 

Metabolism of proline (1) A -pyrroline-5-carboxylate (P5C) synthase (2) ornithine aminotransferase (3) P5C reductase (4) proline oxidase (5) P5C dehydrogenase (6) ornithine decarboxylase. 

Folate deficiency leads to accumulation of Figlu, which is excreted in urine. The excretion is very pronounced after a loading dose of histidine, a test used to detect folate deficiency. More sensitive radioisotopic assays use folate binders to the vitamins. High urinary levels of Figlu may coexist with elevated levels of serum folate. Thus, in vitamin Bn (cobalamin) deficiency, since cobalamin participates in the following reaction, FH4 is trapped as 

N -methyltetrahydrofolate and is unavailable as a carrier for the formimino group of Figlu. 

Similarly, a deficiency of glutamate formiminotransferase leads to accumulation of Figlu and high levels of serum folate. 

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