Three infants with malonic aciduria are reported, one of whom could be studied in detail. All children had severe and progressive encephalopathy with intermittent ketoacidosis and hypoglycemia. One infant died of cardiomyopathy. Biochemical studies revealed that one patient had neither malonyl-CoA decarboxylase nor glutaryl-CoA dehydrogenase deficiencies. This variant of malonic aciduria is different from that of four patients previously reported, both in its clinical and biochemical presentations. The biochemical pathology of this variant malonic aciduria is unknown.

Glycerol kinase activity was found in the particulate fraction of rat brain homogenates predominantly associated with mitochondria. The enzyme remained bound to the particulate fraction after treatment with a variety of solubilizing agents.

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Abstract— Bovine pineal gland S‐adenosylmethionine: N‐acetylserotonin O‐methyltransferase has been purified about 2800‐fold using cell fractionation, ammonium sulphate treatment, Sephadex G‐200 gel filtration and anion exchange chromatography. The enzyme has been found to be a polymer; the smallest unit observed had a mol. wt. of 21,800 and the other polymers' molecular weights were multiples of this figure. In the gland extract polymers of 83,000, 100,000, 125,000 and 150,000 mol. wt. were more abundant than the others; they showed also higher specific activity. One of the products of the reaction, S‐adenosylhomocysteine was found to be a potent inhibitor, whereas the other product, melatonin, did not inhibit the bovine pineal gland enzyme, even at much higher concentrations. Homocysteic acid, cysteic acid, GSG and GSSG inhibited the enzyme. The required concentrations for this effect was 100 times higher than that of S‐adenosylhomocysteine. The addition of GSH to the medium during purification led to complete loss of activity. Adenosine, homocysteine and other thio compounds had little or no effect. The enzyme was found to be activated by its substrates and also by certain anions. Among various organic acid salts, citric acid cycle intermediates were found to be good activators; their nonsubstituted analogues were not as effective. The activator effect of oxaloacetate and bicarbonate was the highest, and was brought about by relatively low concentrations of these anions (1–5 × 10−3 M), hence their effect was considered specific. The degree of activation caused by oxaloacetate was decreased by increasing substrate concentrations and vice versa. The S‐adenosylhomocysteine inhibition could not be reduced by increasing the substrate concentration; S‐adenosylhomocysteine also inhibited the oxaloacetate‐activated enzyme. These observations have been explained by the allosteric behaviour of the enzyme. The kinetic behaviour of various polymers was also investigated. The highest substrate and oxaloacetate activation and the highest S‐adenosylhomocysteine inhibition was observed for polymers of 83,000, 100,000, 125,000 and 150,000 mol. wt. The Km values for S‐adenosylmethionine and N‐acetylserotonin calculated for the oxaloacetate activated enzyme were also lower for these polymers than others.