Rat-Liver Mitochondria and other Subcellular Fractions

1. Rat-liver mitochondria showed a decrease in amino acid production after preparation in 0-25m-sucrose containing EDTA (lnm), but an increase in water content. When EDTA was replaced by Mn2+ (Imm) or succinate (lmM), both amino acid production and water content were lowered, whereas preparation in 0-9% potassium chloride caused an increase in both. 2. Amino acid production by rat-liver homogenates prepared in 0-9% potassium chloride or 0-25M-sucrose was similar (qno aid 0-047 and 0-042 respectively aerobically). After freezing-andthawing q.00o d values were approximately doubled, and approached that of a homogenate prepared in water. 3. All cations tested inhibited amino acid production by mitochondria, Hg2+ and Zn2+ being the most effective in tris-hydrochloric acid buffer. In phosphate buffer Mg2+ and Mn2+ had no effect. Of the anions tested only pyrophosphate and arsenate had any inhibitory effect at final concn. 1 mM. 4. Iodosobenzoate (1 mm) and p-chloromercuribenzenesulphonate (1 mM) inhibited mitochondrial amino acid production by 70-80%, whereas soya-bean trypsin inhibitor, EDTA and di-isopropyl phosphorofluoridate inhibited by a maximum of 30%. Respiratory inhibitors had no effect. 5. Rat-liver homogenate and subcellular fractions each showed an individual pattern ofinhibition when a series of inhibitors