Propionic acid, occurrence

In a similar manner the other amino acids react tyrosine, j3-p-hydroxy-phenyl-a-amino-butyric acid yielding p-hydroxy-phenyl-ethyl alcohol, tyrosol while phenyl-alanine, a-amino-j8-phenyl-propionic acid, yields phenyl-ethyl alcohol. Succinic acid, for example, which is of usual occurrence in fermented liquors is probably formed by a similar reaction from glutamic acid with the additional step of oxidation in the process. 

The first group of contaminants comprises several isomers of mono- and dibrominated (methoxyphenyl)propionic acids. Their occurrence and isomeric distribution is illustrated in Fig. 2. All position isomers with respect to the methoxy group were present. However, for each methoxy substitution (2-, 3- and 4-substitution) only one isomer considering the bromination position was observed in most cases. Just one further monobrominated isomer was detected in the water samples which was not attributed to synthesized reference material. With respect to its mass spectral properties (as discussed above) the occurrence of a further 3-(bromo-2-methoxyphenyl)propionic acid methylester is likely. Interestingly, a very similar isomer pattern of reference substances was obtained by nonselective bromination of the corresponding nonhalogenated compounds (see also Fig. 5). Therefore, a technical preparation of these contaminants can be suggested. 

Additionally, several brominated compounds were identified for the first time as environmental contaminants. Their analytical properties (mass spectral, gas chromatographic and IR spectroscopical data) revealed the occurrence of mono- and dibrominated (methoxyphenyl)propionic acids and hydroxymethylacetophenones. Interestingly, the Rhine water samples investigated were dominated by brominated compounds as compared to chlorinated substances. This is an unusual state of riverine pollution with respect to halogenated compounds. 

Mixtures of Maximum Boiling Point.—The occurrence of mixtures of maximum boiling point (or minimum vapour pressure) is comparatively rare in most of the known cases one of the substances is an acid and the other a base or a compound of basic character—formic, acetic and propionic acid with pyridine (Zawidski) (6), hydrochloric acid with methyl ether (Friedel) (8) or the liquids are water and an acid—formic, hydrochloric, hydrobromic, hydriodic, hydrofiuoric, nitric or perchloric acid (Roscoe) (9) but Ryland finds that such mixtures are formed by chloroform and acetone (A = 4 8 ) and by chloroform and methyl acetate (A =s about 4 3 ) the first observation has been confirmed by Zawidski and by Kuenen and Robson (10), and the second by Miss Fortey (unpublished). 

The occurrence of propionic acid in the rumen has led to a search for members of the propionic acid group. Elsden in 1945 first isolated an organism which was capable of fermenting glucose and lactic acid with the production of acetic and propionic acids. Johns has recently made a detailed study of organisms from the rumen of sheep similar to Vellionella... 

Stjernholm, R. and Wood, H. G. (1960) Glycerol dissimilation and the occurrence of a symmetrical three-carbon intermediate in the propionic acid fermentation. J. Biol. Chem. 235,2757-2761. 

Other acids (often as esters) have been found in fermented molasses. Usually these substances are products of bacteriological action and they are not normal constituents of unfermented molasses. Bauer" oil from the yeast fermentation of Cuban blackstrap consists chiefly of the ethyl esters of capric, lauric, myristic and palmitic acids.122 The fat from the scums of hot-room Louisiana molasses contained hexanoic (caproic) and octanoic (caprylic) acids.10 The occurrence of such volatile acids as propionic,128 butyric128 124 and valeric acids124 requires more adequate establishment. 

Slow oxidation of gaseous methanol. INIany authors have studied the slow oxidation, photochemical or thermal, of gaseous formaldehyde. This reaction is much more complex than that of the acetic or propionic aldehydes the peracid (performic acid) no longer constitutes the principal product of the reaction, and this reaction implies the occurrence of heterogeneous processes (on the vessel walls). It follows (cf. references 2 and 45-47) that this complex oxidation cannot be represented by so simple a mechanism as that which has previously been discussed with regard to other aldehydes. 

Propionyl-CoA is the key intermediate in the formation of the majority of the abnormal urinary metabolites observed in propionic acidaemia and is also responsible for the accumulation of odd-carbon-number fatty acids and abnormal triglycerides and lipids in the disease by competition with acetyl-CoA in fatty acid biosynthesis. The metabolite may also inhibit other enzyme systems, particularly in mitochondria, giving rise to other symptoms. Inhibition of A -acetylglutamate synthetase has been used to explain the hyper-ammonaemia that is frequently observed in patients with propionic acidaemia (Coude et al., 1979), sometimes occurring as the major presenting biochemical abnormality (Harris et ai, 1980). Inhibition of other enzyme systems and of mitochondrial function by propionyl-CoA may well also be responsible for the occasional occurrence of hypoglycaemia in the diseases. Propionyl-CoA accumulation is also Important in the biochemical and clinical presentation of patients with methylmalonic aciduria, the disease described in the next section (11.2). 

Stokke, O., Jellum, E., Eldjam, L. and Schnitler, R. (1973), The occurrence of )8-hydroxy-n-valeric acid in a patient with propionic and methylmalonic acidemia. Clin. Chim. Acta, 45,391. 

Keto acidosis may occur in infants as a result of specific genetic defects, in addition to its occurrence in association with several other organic acidurias, for example propionic acidaemia (ketotic hyperglycinaemia). Chapter 10, Section 10.4.1 on 2-methylacetoacetyl-CoA thiolase deficiency also discussed a report by Robinson et al. (1979) of a patient with apparent combined deficiencies of this enzyme and of 3-oxoacyl-CoA thiolase, which they considered to be identical enzymes. A report of a case of specific 3-oxoacyl-CoA thiolase deficiency has increased interest in these enzymes as causes of congenital keto acidosis, and these are discussed further below, as are patients with a different cause of a similar biochemical condition, succinyl-CoA 3-keto acid-CoA transferase deficiency. 

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