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1. 1. Column and paper Chromatographic procedures are described for the isolation and identification of the carboxylic acid products of amino acid metabolism. 2. 2. Studies of the metabolism of norvaline both in the intact animal and in liver homogenates support the catabolism scheme: norvaline→α-ketovaleric acid→butyric acid→→→acetic acid→→CO 2 .

1. The deposition of casein on a platinum anode which takes place on the passage of a direct current through solutions of alkali caseinates was quantitatively studied, and it was found that: (a) the amount of casein which is deposited is directly proportional to the current, i.e. it obeys Faraday's law; (b) the amount of casein deposited is inversely proportional (within the limits studied) to the amount of alkali which is combined with the casein. 2. A method of determining the transport numbers of proteins insoluble at their isoelectric point has been developed. 3. A titration method for determining the amount of alkali in a casein solution is given. 4. Data from the results of transference experiments on sodium caseinate, potassium caseinate, cesium caseinate, and rubidium caseinate solutions are given. It is shown that the data are best explained on the assumption that in these solutions the carriers of the current are alkali metal cations and casein anions. 5. On the basis of our transference results an explanation is given of the results which were obtained by Robertson and by Haas in their migration experiments.

An enzyme preparation from a strain of Pseudomonas has been purified several hundredfold from sonicate extracts by treatment with butanol, ammonium sulfate, and zone electrophoresis. The enzyme preparation exhibits both glutaminase and asparaginase activities, and no significant separation of the two enzyme activities was achieved by a variety of procedures. The protein(s) has a comparatively low molecular weight of the order of 25,000. The enzyme can be stabilized and kept for long periods frozen in a medium containing 0.01 M borate buffer, 0.01 M acetamide, and 10% glycerol.

Summary1. In acute intoxication experiments with the liver poisons, phosphorus, hydrazine and carbon tetrachloride it was found that phosphorus intoxication almost eliminates the serum calcium rise normally produced by injection of parathyroid extract, hydrazine causes a less marked rise and carbon tetrachloride has no appreciable retarding effect. 2. Since the bone-marrow poison, benzol, causes no alteration in the blood calcium curve following injection of parathyroid extract, the action of phosphorus and hydrazine appears not to be through an injurious action on the bone cells.

The catabolism of dl -α-aminobutyric acid-3- 14 C and of dl -norleucine-3- 14 C have been studied by incubation in rat liver homogenates. Radioactive α-ketobutyric acid and propionic acid were isolated from the α-aminobutyric acid incubations. Radioactive α-ketocaproic acid, valeric acid, and β-hydroxyvaleric acid were isolated from the norleucine incubations. The evidence obtained supports the scheme that the straight-chain α-amino acids are catabolized by conversion to the corresponding α-keto acid, oxidative decarboxylation, and the subsequent oxidation of the resulting monocarboxylic acid by the scheme of β-oxidation.

The enzyme catalyzing the oxidation of imidazolonepropionic acid to hydantoinpropionic acid has been purified about 240-fold from guinea pig liver. A study has been made of some of its properties and of the reaction which it catalyzes. The enzyme exhibits a pH optimum at pH 5.8 and a Michaelis constant of 5 × 10−4 m . It is inhibited by cyanide and to an even greater extent by atabrine, but is insensitive to EDTA. Preparations of the enzyme contained FAD, but this could not be removed without loss of enzymic activity; the addition of FAD to the inactive enzyme did not restore activity. The formation of hydantoinpropionic acid involves the net uptake of 1 μ atom of oxygen per micromole of product formed.

The enzyme from guinea pig liver that catalyzes the oxidation of 4(5)-imidazolone-5(4)-propionic acid to hydantoin-5-propionic acid has been shown to have properties similar to those described for aldehyde oxidase (or so-called xanthine dehydrogenase). The guinea pig liver enzyme catalyzes oxidation of aldehydes, purines, a pyrimidine, and a number of other nitrogen-containing heterocyclic compounds. The ratio of enzyme activity on imidazolone propionate and 4-hydroxypyrimidine remained reasonably constant over a 130-fold enrichment of enzyme purity. The guinea pig liver enzyme responded similarly to activators and inhibitors of the aldehyde oxidases from other sources. The enzyme resembles the so-called xanthine dehydrogenase in that it catalyzes oxidation of purine to 8-hydroxypurine, not 6-hydroxypurine. Utilization of oxygen for the oxidation of hypoxanthine and xanthine is very sluggish, but their oxidation is markedly accelerated by other electron acceptors, e.g., 2,6-dichlorophenolindophenol, as is the case with xanthine dehydrogenase.

Summary1. The cytoplasm of liver has been fractionated by centrifugation in sucrose solution into microsomes, an upper pink mitochondrial layer and a lower normal, yellow mitochondrial layer. These fractions have been studied with respect to amino acid incorporation, cholesterol formation and the ratio of nucleic to protein radioactivity. The mitochondria-P differed sufficiently in these properties from the normal microsomes and mitochondria to be considered a distinct type of cytoplasmic particle. 2. The curve of the ratios of the lower, normal mitochondria to that of the top layer was found to parallel the weight curve of the rat upon aging. The total amount of mitochondria per unit weight of liver remained fairly constant, with the lower fraction increasing and the upper decreasing with age.

Xanthurenic acid-C 14 is not metabolized by the normal rat, even if pyridoxine is injected concomitantly. The total C 14 activity is rapidly excreted in the urine as unchanged XA-C 14 and two XA-C 14 conjugates. The latter compounds appear to contain glucuronide residues at the 8-and 4,8-positions of XA respectively, and the amino acid, serine, is attached at the carboxyl group. The radioactivity from injected XA-C 14 is excreted quantitatively in the urine of rabbits as a single conjugate, in addition to unchanged XA-C 14 . This conjugate is apparently an ethereal sulfate rather than a glucuronide of XA.