A study on the precursors of the acetyl moiety of acetylcholine in brain slices. Observations on the compartmentalization of the acetyl-coenzyme A pool

1. A method was devised for the determination of the specific radioactivity of the acetyl moiety of acetylcholine synthesized from various (14)C-labelled substrates. 2. The precursor for the acetyl moiety of acetylcholine was studied in slices of striatum and cerebral cortex from rat and guinea-pig brain. Incorporation of radioactivity into acetylcholine was determined after incubating the slices in the presence of [2-(14)C]acetate, [(14)C]bicarbonate, [1,5-(14)C]citrate, dl-[1- or 5-(14)C]glutamate or [1- or 2-(14)C]pyruvate. 3. After incubation for 1h, acetylcholine was accumulated significantly in both striatum slices (4.1nmol/mg of protein) and cerebral-cortex slices (0.57nmol/mg of protein) from the rat. Final concentrations were about 11 and 5 times respectively the initial values. 4. With slices from rat striatum, rat cerebral cortex and guinea-pig cerebral cortex, the specific radioactivity of acetylcholine derived from [2-(14)C]pyruvate was very high, reaching approx. 30, 20 and 6% respectively of the initial specific radioactivity of added pyruvate in the medium. With the striatum slices this high value was reached after incubation for 15min. Incorporation of radioactivity from [2-(14)C]acetate was only 1.25, 5.3 and 19.7% of that from [2-(14)C]pyruvate in rat striatum, rat cerebral-cortex and guinea-pig cerebral-cortex slices respectively. A small but definite incorporation was found from [5-(14)C]glutamate. No incorporation was found from the other substrates. The findings suggest that pyruvate is the most important precursor for the synthesis of the acetyl moiety of acetylcholine in brain slices. 5. The specific radioactivity of acetylcholine relative to that of citrate when [2-(14)C]pyruvate was used compared with that obtained when [2-(14)C]acetate was used. A marked difference was found in all slices, suggesting metabolic compartmentation of the acetyl-CoA pool.

Purification and properties of acid phosphomonoesterase from human parotid saliva

Acid phosphomonoesterase was separated from human parotid saliva and purified. The purified enzyme was proved homogeneous on sedimentation and disk electrophoresis. The optimal pH of the enzyme was 3.3. The enzyme had no substrate specificity for phosphomonoesters and its activity was inhibited by SnF2 or NaF.

Citrate synthase activity in periodontal tissues

SYNOPSIS IN INTERLINGUA

ACTIVITATE DE SYNTHASE DE CITRATO IN Tissu PERIODONTAL.—Con le utilisation del sensibile e convenibile essayo a fissura per ester thiolic, le activitate de synthase de citrato (EC 4.1.3.7; oxaloacetato-lyase de citrato) esseva determinate in le fractiones supematante de gingiva, osso alveolar, e altere tissus de porco de India. Cortice de femore, osso alveolar, gingiva, hepate, e ren possedeva approximativemente 1/60, 1/33, 1/24, 1/12, e 1/4, respectivemente, le activitate medie per mg de extrahite proteina cardiac. Le activitate exprimite a base de unitates de peso de tissu humide esseva etiam le plus alte pro le corde. Illo de osso alveolar e de gingiva esseva approximativemente 1/440 e 1/40, respectivemente, del correspondente valor trovate pro le corde.