Energy metabolism in the brains of L-phenylalanine-treated chicks

Abstract— When day-old chicks were injected intraperitoneally with 1.62mmoles of l -phenylalanine, they developed a condition resembling narcosis. Simultaneously, whole brain levels of phenylalanine were 2–4 μmol/g, whereas those in control brain were 0.06 μmol/g. Examination of some glycolytic intermediates in the brain revealed significant decreases in fructose-1,6-diphosphate, l -α-glycerol phosphate and lactate, in comparison to the levels of these compounds in the saline-injected control animals. Levels of glucose and glucose-6-phosphate either increased or did not change, whereas levels of glycogen did not differ significantly. Phosphocreatine increased reciprocally with the decrease in inorganic phosphate. The levels of adenine nucleotide (energy charge) were not affected. Utilization of cerebral high-energy phosphates was depressed by 50–70 per cent when determined as a function of metabolic rate in the brain at 15- and 30-s periods of ischaemia according to the ‘closed-system’ technique. Explanations for these data have been examined, such as toxicity of phenylacetate and inhibition of glycolytic enzymes by phenylpyruvate and l -phenylalanine and their relevance to this study is discussed.     

FOLATE LEVELS IN DEVELOPING MOUSE BRAIN1

Abstract— The folate coenzymes of mouse brain underwent quantitative and qualitative changes during the first few weeks after birth. The total folate coenzymes per unit wet weight declined by approximately 60 per cent. In the newborn brains a relatively small proportion of the total folates were poly-γ-glutamyl derivatives, but the percentage of the total folates in these forms increased as the brain matured.     

The number of catalytic sites in acetylcholinesterase

By using two methods of titration, the number of active sites in acetylcholinesterase was determined. Either stepwise inhibition of the enzyme by an irreversible inhibitor, namely di-isopropyl phosphorofluoridate, or direct measurement of the concentration of active sites by titration with o-nitrophenyl dimethylcarbamate yielded an equivalent weight of approx. 130000 for an active site in acetylcholinesterase. This indicates two sites per molecule, since the native enzyme has a molecular weight of 260000.