Transmethylation of homocysteine to methionine: efficiency in the rat and chick.
Experiments were conducted with young chicks and rats to quantify the efficacy of L-homocysteine as a methionine precursor. Linear growth responses were obtained to both L-methionine and L-homocysteine when added to a methionine-deficient intact-protein diet containing a plethora of cystine. Slope-ratio multiple regression methodology indicated L-homocysteine to be 64.5% as efficacious as L-methionine in rats and 62.5% as efficacious in chicks. Plasma-free methionine also increased linearly as graded levels of either L-methionine or L-homocysteine were added to the diet of rats. At higher dosages of L-homocysteine, betaine, but not choline, showed some efficacy in enhancing the conversion of homocysteine to methionine. In the linear response surface of the growth curve, however, supplemental betaine was without effect on L-homocysteine bioefficacy, as was also the case for supplemental sarcosine and N5-methyltetrahydrofolic acid.
Baker
D H
DH
Czarnecki
G L
GL
D000818:Animals; D001622:Betaine / Q000008:administration & dosage / Q000494:pharmacology; D001835:Body Weight; D002645:Chickens; D002794:Choline / Q000008:administration & dosage / Q000494:pharmacology; D004032:Diet; D006710:Homocysteine / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000096:biosynthesis* / Q000097:blood; D008745:Methylation; D051381:Rats; D011919:Rats, Inbred Strains; D012521:Sarcosine / Q000008:administration & dosage / Q000494:pharmacology; D013763:Tetrahydrofolates / Q000008:administration & dosage / Q000494:pharmacology
D013763:Tetrahydrofolates; D006710:Homocysteine; D001622:Betaine; D008715:Methionine; D002794:Choline; C005984:5-methyltetrahydrofolate; D012521:Sarcosine