Alterations in the chain length of pteroylpoly-γ-glutamates and in the activity of pteroylpoly-γ-glutamate hydrolase in response to changes in the steady state of one carbon metabolism

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Abstract
The effect of a high protein diet and of limiting dietary methionine and choline on the relative proportions of the various pteroylpoly-γ-glutamates, conjugase activity, and folate content in liver of male Japanese quail was determined. After 14 days on the diets all birds were injected with [3′,5′,9(n)-3H] folic acid and killed 72 hr later. The extracted liver folates were oxidatively cleaved to their p-aminobenzoylpoly-γ-glutamates (pABGn) and resolved by DEAE cellulose chromatography. Polyglutamates with 4,5,6, and 7 glutamyl residues were found in the livers of all the dietary groups, pABG5 being the predominant form. Differences in the relative proportions of the various chain length polyglutamates as a result of the different diets were observed. As a percentage of the total pABGn pool the pABG5 was 47% in the 88% casein group (high protein, methionine-choline sufficient), 64% in the 25% casein group (methionine limiting, choline sufficient), 70% in the 25% casein choline-free group (methionine limiting, choline deficient), and 56% in the 23.3% casein plus 1.7% methionine group (methionine-choline sufficient). Conjugase activity was highest in the 88% casein, and 23.3% casein plus 1.7% methionine groups, lower in the 25% casein group, and lowest in the 25% casein choline-free group. There was a 2-fold increase in total folate content in the livers of birds fed the 88% casein diet as compared to the 25% casein groups. The data indicate that methionine and choline deficiency alter the pteroylpolyglutamate distribution towards an increase in pentaglutamate forms.