Dissimilation of Carbon Monoxide to Acetic Acid by Glucose-Limited Cultures of Clostridium thermoaceticum

Clostridium thermoaceticum was cultivated in glucose-limited media, and the dissimilation of CO to acetic acid was evaluated. We found that cultures catalyzed the rapid dissimilation of CO to acetic acid and CO₂, with the stoichiometry obtained for conversion approximating that predicted from the following reaction: 4CO + 2H₂O → CH₃CO₂H + 2CO₂. Growing cultures formed approximately 50 mmol (3 g) of CO-derived acetic acid per liter of culture, with the rate of maximal consumption approximating 9.1 mmol of CO consumed/h per liter of culture. In contrast, resting cells were found not to dissimilate CO to acetic acid. ¹⁴CO was incorporated, with equal distribution between the carboxyl and methyl carbons of acetic acid when the initial cultivation gas phase was 100% CO, whereas ¹⁴CO₂ preferentially entered the carboxyl carbon when the initial gas phase was 100% CO₂. Significantly, in the presence of saturating levels of CO, ¹⁴CO₂ preferentially entered the methyl carbon, whereas saturating levels of CO₂ yielded ¹⁴CO-derived labeling predominantly in the carboxyl carbon. These findings are discussed in relation to the path of carbon flow to acetic acid.     

Calcium binding by human erythrocyte membranes. Significance of carboxyl, amino and thiol groups

1. The role of the ionized carboxyl groups of proteins of the erythrocyte membrane as Ca(2+) receptor sites was investigated. A water-soluble carbodi-imide [1-cyclohexyl-3-(2-morpholinoethyl)carbodi-imide methotoluene-p-sulphonate], referred to as carbodi-imide reagent, and glycine methyl ester were used to modify the free carboxyl groups of the membrane. The degree of modification was estimated from amino acid analyses, which showed the amount of glycine incorporated. As the concentration of carbodi-imide reagent was raised (0.1-0.4m) incorporation of glycine increased and Ca(2+) binding decreased by about 77%. At 0.4m-carbodi-imide reagent all of the binding of Ca(2+) to protein was abolished and it was estimated that about 37% of the side-chain carboxyl groups of aspartic acid plus glutamic acid had been blocked by glycine. 2. Acetylation of all of the free amino groups was achieved by incubating the erythrocyte ;ghosts' at pH10.3 with acetic anhydride (10-15mg/10mg of ;ghost' protein). Acetylation increased by 1.5-fold the capacity of the ;ghost' to bind Ca(2+), indicating that the remaining carboxyl groups of aspartic acid and glutamic acid were made available for Ca(2+) binding by this procedure. These findings support the concept that in normal ;ghosts', at pH7.4, Ca(2+) binding to free carboxyl groups is partially hindered by the presence of charged amino groups. 3. Treatment of ;ghosts' with N-acetylneuraminidase, which removed 94% of sialic acid residues, and treatment with 1mm-p-chloromercuribenzoate did not alter Ca(2+) binding. The major effect of 5.8mm-p-chloromercuribenzoate upon ;ghosts' was to cause a solubilization of a calcium-membrane complex, which included about one-third of the ;ghost' protein. The molar ratio of Ca(2+): protein in the solubilized material was the same as that in the intact (untreated) ;ghosts'.     

The C4-dicarboxylic acid pathway of photosynthesis. Identification of intermediates and products and quantitative evidence for the route of carbon flow

1. When leaves with the C(4)-dicarboxylic acid pathway of photosynthesis are exposed to (14)CO(2) the major labelled compounds formed, in order of labelling, are dicarboxylic acids, 3-phosphoglycerate, bexose phosphates and sucrose. During the present studies several quantitatively minor intermediates were identified and their labelling behaviour is described. 2. The pattern of labelling of dihydroxyacetone phosphate, fructose 1,6-diphosphate and ribulose di- and mono-phosphates during radiotracer pulse-chase experiments was consistent with their operation as intermediates in the pathway of carbon dioxide fixation. 3. Serine, glycine, alanine and glutamate had labelling patterns typical of products secondary to the main flow of carbon. 4. The mechanism of the transfer of label from C-4 of dicarboxylic acids to C-1 of 3-phosphoglycerate was also examined. Evidence consistent with pyruvate being derived from C-1, C-2 and C-3 of oxaloacetate, and for a relationship between ribulose 1,5-diphosphate and the acceptor for the C-4 carboxyl group, was obtained. 5. Evidence is provided that, under steady-state conditions, essentially all the label incorporated from (14)CO(2) into C-1 of 3 phosphoglycerate enters via C-4 of the dicarboxylic acids. These and other studies indicated that the route via dicarboxylic acids is essentially the sole route for entry of carbon into 3-phosphoglycerate.     

Biosynthesis of amino acids in Clostridium pasteurianum

1. Clostridium pasteurianum was grown on a synthetic medium with the following carbon sources: (a) (14)C-labelled glucose, alone or with unlabelled aspartate or glutamate, or (b) unlabelled glucose plus (14)C-labelled aspartate, glutamate, threonine, serine or glycine. The incorporation of (14)C into the amino acids of the cell protein was examined. 2. In both series of experiments carbon from exogenous glutamate was incorporated into proline and arginine; carbon from aspartate was incorporated into glutamate, proline, arginine, lysine, methionine, threonine, isoleucine, glycine and serine. Incorporations from the other exogenous amino acids indicated the metabolic sequence: aspartate --> threonine --> glycine right harpoon over left harpoon serine. 3. The following activities were demonstrated in cell-free extracts of the organism: (a) the formation of aspartate by carboxylation of phosphoenolpyruvate or pyruvate, followed by transamination; (b) the individual reactions of the tricarboxylic acid route to 2-oxoglutarate from oxaloacetate; glutamate dehydrogenase was not detected; (c) the conversion of aspartate into threonine via homoserine; (d) the conversion of threonine into glycine by a constitutive threonine aldolase; (e) serine transaminase, phosphoserine transaminase, glycerate dehydrogenase and phosphoglycerate dehydrogenase. This last activity was abnormally high. 4. The combined evidence indicates that in C. pasteurianum the biosynthetic role of aspartate and glutamate is generally similar to that in aerobic and facultatively aerobic organisms, but that glycine is synthesized from glucose via aspartate and threonine.     

Biosynthesis of slaframine, (1S,6S,8aS)-1-acetoxy-6-aminooctahydroindolizine, a parasympathomimetic alkaloid of fungal origin. 3. Origin of the pyrrolidine ring.

The phytopathogen Rhizoctonia leguminicola has previously been shown to incorporate pipecolic acid into the piperidine alkaloids 1-acetoxy-6-aminooctahydroindolizine (slaframine) and 3,4,5-trihydroxyoctahydro-1-pyrindine. In the experiments described here, resting cultures of R. leguminicola were incubated with [1-14C]- and [2-14C]malonic acid and with [1-14C]- and [2-2H]acetic acid. Both acids were incorporated into the ring systems of both alkaloids. Mass spectrometric analysis of 2H-enriched slaframine showed that the label resides in the five-membered ring and that the methyl carbon of acetate is joined to the carboxyl carbon of pipecolate. A pipecolate-dependent decarboxylation of [1-14C]malonate was demonstrated in cell-free extracts of R. leguminicola. The results account for previously unattributed carbons in the two alkaloids and suggest the formation of an eight-carbon intermediate common to both alkaloids by acylation of malonate with pipecolic acid.     

Biosynthesis of an unusual amino acyl moiety contained in bestatin

The biosynthetic pathway of an unusual amino acyl [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl (AHP)] moiety which is contained in bestatin has been studied by testing the incorporation of potential precursors. L-[U-14C]-Phenylalanine, L-[U-14C]leucine, and [U-14C]acetic acid were efficiently incorporated into bestatin, but the radioactivity of L-[1-14C]phenylalanine, [1-14C]glyoxylic acid, and [14C]oxalic acid were not incorporated. Incorporation of acetic acid into 1- and 2-carbon of the AHP moiety was confirmed by incorporation of [13C]acetic acid. Thus, the AHP moiety was shown to be biosynthesized from L-phenylalanine and two carbon atoms of acetic acid, accompanied by decarboxylation of the phenylalanine.     

Synthesis of Terpene Alcohol Esters by Lipase

The metabolic fates of the carbon skeletons of L-(U-¹⁴C)arginine, proline and glutamic acid were investigated in growing rats fed with diets containing different percentages of protein calories (0, 5, 10, 15 and 30 PC%) at 4100 kcal of metabolizable energy per kg of diet.

The incorporation of ¹⁴C into body protein at 12hr after the injection of ¹⁴C-arginine was more than 50% of the dose in all dietary groups, showing a high efficiency of utilization of this amino acid for protein synthesis. The incorporation of ¹⁴C into body protein from ¹⁴C-proline was most increased in the 15 PC% group, and the values were reduced in rats fed with lower and higher PC% diets. The carbon skeleton of ¹⁴C-glutamic acid was extensively oxidized to expired carbon dioxide, and the ¹⁴C incorporation into body protein was markedly less. The pattern of expired ¹⁴C0₂ production from each ¹⁴C-amino acid was in inverse proportion to that of ¹⁴C incorporation into body protein. The results indicate that the metabolic responses of arginine, proline and glutamic acid to dietary protein change at 10 to 15 PC%, where the growth rate reached its approximate maximum.     

Photosynthesizing Leaves and Nodulated Roots as Donors of Carbon to Protein of the Shoot of the Field Pea (Pisum arvense L.)

In Pisum arvense, the amides and amino-acids normally suppliedto the shoot in the transpiration stream transfer carbon toprotein largely throught the amino-acids, aspartic acid (+asparagine),glutarnic acid (+glutamine), threonine, lysine, arginine, andproline. Carbon from carbon dioxide enters the protein of photosynthesizingtissues through an essentially complementary set of amino-acidsincluding glycine, alanine, serine, valine, and the aromaticamino-acids tyrosine, phenylalnine, and histidine. Young tissuesof the shoot synthesize certain amino-acids de novo by metabolismof sugars supplied from photosynthesizing leaves. Each mature leaf on a shoot contributes carbon to current synthesisof protein at the shoot apex. Sucrose accounts for more than90 per cent of the labelled carbon leaving any age of leaf whichhas been fed with ¹⁴CO₂. Upper leaves supply labelled assimilatesdirectly to the shoot apex, and the radiocarbon from these assimilatesis subsequently incorporated into a wide range of amino-acidunits of protein. The majority of the labelled assimilates exportedfrom a lower leaf move downwards to the root and nodules and,in consequence, the amino-acids and amides associated with rootmetabolism are strongly represented among the compounds eventuallylabelled in the apical region of the shoot.     

The synthesis of amino acids by Methanobacterium omelianskii

1. Methanobacterium omelianskii was grown on (14)CO(2) and unlabelled ethanol, or on [1-(14)C]- or [2-(14)C]-ethanol and unlabelled carbon dioxide. The cell protein was hydrolysed and certain of the amino acids were isolated and degraded. 2. Carbon from both carbon dioxide and ethanol is used for biosynthesis of amino acids, and in most cases ethanol is incorporated as a C(2) unit. Ethanol carbon atoms and carbon dioxide carbon atoms apparently enter the same range of compounds. Ethanol and carbon dioxide are equally important as sources of cell carbon. 3. The origins of carbon atoms of aspartate, alanine, glycine, serine and threonine are consistent with the synthesis of these amino acids, by pathways known to exist in aerobic organisms, from pyruvate arising by a C(2)+C(1) condensation. The proportion of total radioactivity found in C-1 of lysine, proline, methionine and valine is consistent with synthesis of these amino acids by pathways similar to those found in Escherichia coli. Isoleucine is probably formed by carboxylation of a C(5) precursor formed entirely from ethanol. Glutamate is formed by an unknown pathway.     

Biotin carboxyl carrier protein in barley chloroplast membranes.

Biotin localized in barley chloroplast lamellae is covalently bound to a single protein with an approximate molecular weight of 21 000. It contains one mole of biotin per mole of protein and functions as a carboxyl carrier in the acetyl-CoA carboxylase reaction. The protein was obtained by solubilization of the lamellae in phenol/acetic acid/8 M urea. Feeding barley seedlings with [14C]-biotin revealed that the vitamin is not degraded into respiratory substrates by the plant, but is specifically incorporated into biotin carboxyl carrier protein.     

Distribution of isotopic label after the oral administration of free and bound 14C-labelled glucosamine in rats

The metabolic fate of [1-(14)C]glucosamine, of N-acetyl[1-(14)C]glucosamine and of glycoproteins labelled with [1-(14)C]glucosamine was studied in rats for a period of 24hr. after these materials were given orally or injected. When [1-(14)C]glucosamine was injected 26.3% of the label was excreted in the urine, 19.7% was expired as carbon dioxide and 12.7% was incorporated into plasma proteins. When the same compound was given orally, 49.2% of the label was expired as carbon dioxide, with little appearing in the urine or in the plasma. When N-acetyl[1-(14)C]glucosamine was injected, 51.3% of the label was excreted in the urine with 12.3% appearing in carbon dioxide, but there was little incorporation into plasma protein. When this compound was given orally, 46.5% of the label was expired as carbon dioxide, 7.4% was recovered in the urine and 1.7% was incorporated into plasma protein. After the injection of (14)C-labelled glycoprotein 21.0% of the label was expired as carbon dioxide, whereas when it was given orally 49.8% of the label was recovered in carbon dioxide. The differences observed between the metabolic fate of the amino sugars when they were given orally and their fate when injected could not be accounted for by the action of the intestinal microflora or by the rate of administration of the material. It is concluded that amino sugars undergo metabolic alteration or degradation during absorption.     

The metabolism of glyoxylate by cell-free extracts of Pseudomonas sp

1. Extracts of Pseudomonas sp. grown on butane-2,3-diol oxidized glyoxylate to carbon dioxide, some of the glyoxylate being reduced to glycollate in the process. The oxidation of malate and isocitrate, but not the oxidation of pyruvate, can be coupled to the reduction of glyoxylate to glycollate by the extracts. 2. Extracts of cells grown on butane-2,3-diol decarboxylated oxaloacetate to pyruvate, which was then converted aerobically or anaerobically into lactate, acetyl-coenzyme A and carbon dioxide. The extracts could also convert pyruvate into alanine. However, pyruvate is not an intermediate in the metabolism of glyoxylate since no lactate or alanine could be detected in the reaction products and no labelled pyruvate could be obtained when extracts were incubated with [1-¹⁴C]glyoxylate. 3. The ¹⁴C was incorporated from [1-¹⁴C]glyoxylate by cell-free extracts into carbon dioxide, glycollate, glycine, glutamate and, in trace amounts, into malate, isocitrate and α-oxoglutarate. The ¹⁴C was initially incorporated into isocitrate at the same rate as into glycine. 4. The rate of glyoxylate utilization was increased by the addition of succinate, α-oxoglutarate or citrate, and in each case α-oxoglutarate became labelled. 5. The results are consistent with the suggestion that the carbon dioxide arises by the oxidation of glyoxylate via reactions catalysed respectively by isocitratase, isocitrate dehydrogenase and α-oxoglutarate dehydrogenase.     

The Incorporation of 14CO2 into Green Peas in the Dark

Shelled green peas (ripening seeds of Pisum sativum var. Onward)were kept in the dark for 2 or 3 days in an atmosphere, eitherof air or 10 per cent carbon dioxide in air, containing ¹⁴CO₂.Samples were removed at intervals, the acids of the T.C.A.C.extracted, estimated, and their content of ¹⁴C measured. Incorporationof ¹⁴C was mainly into the carboxyl carbon atoms of the acidswhich, with the exception of citrate, rose in specific activityrapidly for the first 4–6 h and then levelled off androse slowly for the rest of the experiment. The final valuesattained, again with the exception of C-6 of citrate, were muchbelow that of the tissue carbon dioxide. The cause of this failureto equilibrate with tissue carbon dioxide is discussed. Twomain carboxylation reactions are proposed, one from pyruvate(or other three carbon acid) to malate and the other from -oxoglutarateto oxalsuccinate and so to C-6 of citrate. The value of thevelocity constant of the first of these reactions was shownto be markedly decreased by increase in tissue carbon dioxidewhile that for the second carboxylation was unaffected. ¹⁴Cmoved into soluble amino-acids rapidly at first and then moreslowly; protein received ¹⁴C at a high rate throughout the experimentsmainly by isotopic exchange reactions. Calculations were madeof the rate of movement of carbon in the T.C.A.C. which wouldhave been required to give the observed changes in specificactivity of the metabolites but no scheme tested fitted allthe results satisfactorily.     

Chemical modification of a functional arginine residue of rat liver glycine methyltransferase

Rat liver glycine methyltransferase is inactivated irreversibly by phenylglyoxal in potassium phosphate buffer. The inactivation obeys pseudo-first-order kinetics, and the apparent first-order rate constant for inactivation is linearly related to the reagent concentration. A second-order rate constant of 10.54 +/- 0.44 M-1 min-1 is obtained at pH 8.2 and 25 degrees C. Amino acid analysis shows that only arginine is modified upon treatment with phenylglyoxal. Sodium acetate, a competitive inhibitor with respect to glycine, affords complete protection in the presence of S-adenosylmethionine. Acetate alone has no effect on the rate of inactivation. The value of the dissociation constant for acetate determined from the protection experiment is in good agreement with that obtained by kinetic analysis. Comparison of the amount of [14C]phenylglyoxal incorporated into the protein and the number of arginine residues modified in the presence and absence of protecting ligands indicates that modification of one arginine residue per enzyme subunit eliminates the enzyme activity, and this residue is identified as Arg-175 by peptide analysis. The arginine-modified glycine methyltransferase appears to bind S-adenosylmethionine as the native enzyme does, as seen from quenching of the protein fluorescence by S-adenosylmethionine. These results suggest the requirement of Arg-175 in binding the carboxyl group of the substrate glycine.     

Relationship between intracellular amino acids and protein synthesis in the extensor digitorum longus muscle of rats

1. The incorporation into protein, and the accumulation into the free amino acid pools, of radioactive l-leucine and glycine was studied in rat extensor digitorum longus muscle. 2. The tissue was incubated first with (14)C-labelled and then with (3)H-labelled amino acid. 3. The experimental results were consistent with a model based on the premise that the amino acids in protein were incorporated directly from the extracellular pool.     

Studies of Glycollate Utilization and Some Associated Enzymes of C1 Metabolism in the Endosperm of Ricinus communis L.

Glycollate metabolism in 5-day-old endosperm tissues of Ricinuscommunis L. was examined by feeding micromolar quantities of[2-¹⁴C]glycollate to tissue slices. It was found that glycollatecarbon was rapidly incorporated into glyoxylate, glycine, serine,and carbon dioxide. Only small amounts of ¹⁴C were incorporatedinto the sugars. Changes in the distribution of ¹⁴C with timesuggested that glyoxylate was a primary product and that glycineand serine were secondary products of glycollate metabolism.The results of feeding experiments are interpreted as indicatingthat a glycollate pathway leading to sugar biosynthesis is ofminor importance compared to the rapid utilization of glycollatefor the biosynthesis of glycine and serine. Enzymes necessaryto catalyse the incorporation of glycollate into glycine andserine have been examined in castor-bean endosperm extracts.These included: glycollic acid oxidase, gloxylic acid reductase,glyoxylate transaminase, N¹⁰ formyltetrahydrofolate synthetase,N⁵,N¹⁰-methylenetetrahydrofolate dehydrogenase, and serine hydroxymethyltransferase.     

Specific modification of the carboxyl groups of hemoglobin S

The reactivity of the carboxyl groups of hemoglobin S to form amide bonds with glycine ethyl ester by carbodiimide-activated coupling, and the influence of this derivatization on the functional properties of the protein have been investigated. Incubation of carbonmonoxy or oxyhemoglobin S with 20 mM 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide in the presence of 100 mM [14C]glycine ethyl ester, at pH 6.0 and 23 degrees C for 1 h resulted in the modification of, on an average, three carboxyl groups of the protein. The Hill coefficient of the modified hemoglobin S was 2.7, indicating normal subunit interactions. The derivatization increased the oxygen affinity of the molecule (the P50 was lowered from 8.0 to 5.0). The derivatization also resulted in an increase in the minimum gelling concentration of hemoglobin S from 16 to 24 g/100 ml. The reaction conditions used for the derivatization of the carboxyl groups of hemoglobin S are very selective for the protein carboxyl groups; very little of the label is associated with the heme carboxyls. Tryptic peptide mapping of the modified hemoglobin S indicated that the peptide beta T5, i.e. the segment representing amino acid residues 41 to 59 of beta-chain, accounted for nearly 75% of the label associated with the globin, demonstrating the high selectivity of the derivatization. Sequence analysis of the derivatized beta T5 demonstrated that at least 65% of the label incorporated into hemoglobin S is targeted toward the carboxyl group of Glu-43(beta), identifying it as the most reactive carboxyl group in hemoglobins. The results suggest that modification of the carboxyl group of hemoglobins S, presumably the gamma-carboxyl of Glu-43(beta), reduces the propensity of deoxyhemoglobin S to polymerize.     

Growth-promoting Activity of an Aqueous Extract of Soybean Seeds for Some Microorganisms

The metabolic fates of the carbon skeletons of leucine, lysine, and threonine were studied in growing rats on the diets containing graded levels of protein calorie percentages (10, 20, 30, and 40PC%) by use of either gluten or zein at 4100 kcal of metabolizable energy per kg of diets. In growth experiment for 21 days, body weight gain, food intake, and body fat increased at higher PC% in the gluten diets, but rats given zein did not maintain their initial weight even at 40PC%. The concentration of plasma free lysine remained low with the zein diets, but plasma threonine increased at 10 and 20PC% in the gluten and zein diets, respectively. Plasma leucine increased as the protein level increased either dietary protein. More than 70% of ¹⁴C was incorporated into body protein 12 h after an intraperitoneal injection of labeled lysine in all groups, but little ¹⁴CO₂ was expired in rats on the gluten and zein diets. About 79% of ¹⁴C-threonine was incorporated into body protein in rats given the gluten and zein diets at 10PC%, but the values were gradually decreased with increasing the dietary protein levels. Some 40–50% of ¹⁴C-leucine was incorporated into the body protein in rats given the gluten diets, and the values for the zein diets were extensively decreased in the higher PC% groups where the expired ¹⁴CO₂ was inversely increased to a great extent. These results showed that, when a specific amino acid was limiting or deficient in the diet, the major portion of the labeled amino acid was utilized for body protein synthesis and little was oxidized to carbon dioxide, whereas the oxidative degradation of essential amino acid other than limiting one was increased and the efficiency of the amino acid utilization was relatively decreased.     

Influence of amino acids and organic antimetabolites on growth and biosynthesis of the chemoautotroph Thiobacillus neapolitanus strain C

Summary The growth of Thiobacillus neapolitanus strain C in liquid cultures was depressed by phenylalanine, p-fluorophenylalanine, cysteine, methionine, nor-leucine, azetidine-2-carboxylic acid, and chloramphenicol, but was little affected by glutamic acid, glycine, proline, azathymine, or oligomycin.Growing cultures assimilated ¹⁴C-labelled glycine, glutamic acid, phenylalanine, and tyrosine into protein. Tyrosine and phenylalamine were incorporated unchanged, but glutamate was used also for synthesis of arginine and proline. Glycine-¹⁴C contributed also to adenine and guanine synthesis. The extremely large amounts of phenylalanine incorporated into protein could indicate its toxicity to depend on its producing abnormal protein synthesis. Azetidine-2-carboxylic acid appeared to lower the amount of proline in the protein.Assimilation of glutamate and glycine by non-growing organisms was almost entirely dependent on energy from thiosulphate oxidation, thus suggesting a cause of obligate chemoautotrophy. Chloramphenicol specifically inhibited this thiosulphate-dependent incorporation of glutamate, glycine or CO₂ into protein at concentrations which did not affect total CO₂-fixation. Provided that energy is available from thiosulphate-oxidation this Thiobacillus is thus able to (a) activate exogenous amino acids; (b) incorporate them and CO₂ into protein by a chloramphenicol sensitive mechanism; (c) synthesise proline and arginine from glutamate; or adenine and guanine from glycine. Its biosynthesis thus depends on mechanisms like those of heterotrophs but requires to be driven by a chemolithotrophic energy supply.     

Ethanolamine Metabolism in Plant Tissues

Ethanolamine is readily metabolized by oat, pea, wheat, apple and carrot tissue preparations. Ethanolamine-1,2 (14)C was incorporated into the lipid fraction, and (14)C activity was distributed in the organic acid, sugar, acid volatile, carbon dioxide and insoluble residue fractions. The distribution varied with the particular tissue. Incorporation into the lipid fraction occurred in tissue homogenates in the absence of ATP by a Ca(++) activated system similar to that reported for animal preparations. The initial step in ethanolamine oxidation involves an amine oxidase. Glycolaldehyde and glyoxylic acid are metabolic intermediates, the former in the conversion of ethanolamine to carbon dioxide. No evidence was obtained for the operation of an ethanolamine transaminase or for the involvement of phosphorylated intermediates in the conversion of ethanolamine to carbon dioxide.