Propionic acid oxidase

The production of substances that preserve the food from contamination or from oxidation is another important field of membrane bioreactor. For example, the production of high amounts of propionic acid, commonly used as antifungal substance, was carried out by a continuous stirred-tank reactor associated with ultrafiltration cell recycle and a nanofiltration membrane [51] or the production of gluconic acid by the use of glucose oxidase in a bioreactor using P E S membranes [52]. Lactic acid is widely used as an acidulant, flavor additive, and preservative in the food, pharmaceutical, leather, and textile industries. As an intermediate product in mammalian metabolism, L( +) lactic acid is more important in the food industry than the D(—) isomer. The performance of an improved fermentation system, that is, a membrane cell-recycle bioreactors MCRB was studied [53, 54], the maximum productivity of 31.5 g/Lh was recorded, 10 times greater than the counterpart of the batch-fed fermentation [54]. 

Roulier et al. reported a sensitive and specific method for the measurement of choline and hydrogen peroxide in sea-water [45]. Choline was oxidized by choline oxidase to produce betaine and H202. The latter was used with horse-radish peroxidase to oxidize hydro-xyphenyl-propionic acid to produce a fluorescent diphenol end product. The resulting fluorescence at 410 nm (excitation at 320 nm) was proportional to the amount of H202, and could thus be used to measure the amount of choline present in the sample. Only 2-dimethyl aminoethanol interfered. The method was optimized, and used to determine 0 15 nM choline in coastal sea-water. 

List of Abbreviations Ach, acetylcholine AMPA, a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid CNS, central nervous system COMT, catechol-O-methyltransferase DA, dopamine DRP-2, dihy-dropyrimidinase-related protein 2 DSM, diagnostic and statistical manual of mental disorders GNAS1, guanine nucleotide-binding protein (G-protein) alpha stimulating activity polypeptide 1 5-HIAA, 5-hydroxyindole acetic acid 5-FIT, serotonin (5-hydroxytryptamine) MAO, monoamine oxidase MHPG, 3-methoxy-4-hydroxyphenylglycol NE, norepinephrine NMDA, N-methyl-D-aspartate PCP, phencyclidine SSRI, selective serotonin reuptake inhibitor SDS, schedule for the deficit syndrome... 

Mitochondrial coproporphyrinogen oxidase is localized in the intermembrane space and is probably loosely bound to the outer surface of the inner membrane. It catalyzes the successive conversion of propionic acid groups of ring A and ring B to vinyl groups (Figure 29-7). 

Staple et al. showed that the conversion of 3a,7a,12a,24-tetrahydroxy-5/8-cholestanoic acid into cholic acid (cf. Fig. 3) can occur in rat liver microsomes or in cytosolic fractions fortified with NAD" or NADP and that propionic acid is released [42,43]. Pedersen and Gustafsson showed recently that the peroxisomal fraction had a high capacity to convert 3a,7a,12a-trihydroxy-5 8-cholestanoic acid into cholic acid [150]. Later, Kase et al. found that the peroxisomal fraction was more active than the microsomal and the mitochondrial fractions and that 3a,7a,12a-24-tetrahydroxy-5j8-cholestanoic acid was an intermediate in the conversion [151]. Thus, some of the previous contradictory results may be explained by varying degrees of contamination of the microsomal and mitochondrial fractions with peroxisomes. In the work by Kase et al. it was shown that the over-all conversion of 3a,7a,12a-trihydroxy-5 -cholestanoic acid into cholic acid in the peroxisomes was absolutely dependent upon the presence of Mg ", CoA, ATP and NAD. The reaction was stimulated by FAD, by cytosolic protein, by microsomal protein and by bovine serum albumin. It is possible that the stimulatory effect of the microsomes and cytosol was imspecific and due to the increased protein concentration per se. The stimulatory effect of FAD was taken as evidence that 3a,7a,12a-tri-hydroxy-5yS-cholestanoyl-CoA oxidase is a FAD-containing protein. There was a lag phase in the reaction, possibly due to the activation step, and it was suggested that the activation was rate limiting. Also in this case, it was not possible to isolate a A -unsaturated intermediate in the reaction. The participation of a desaturase and a hydratase was proved by the incorporation of from H20 into 3a,7a,12a,24-te-trahydroxy-5/8-cholestanoic acid (Bjorkhem, Kase and Pedersen, unpublished study). 

Over 20 years ago, monoamine oxidase inhibitors of the hydrazine type were proposed as supplementary hypoglycaemic agents for treatment of diabetes mellitus [ 130-133]. Due to their toxicity, this approach was abandoned [134], only to be rekindled by a group at the Institut fUr Klinische Chemie [ 135, 136], They found two hydrazine analogues, (2-phenylethylhydrazono)- and 2-(cyclo-hexylethylhydrazono)propionic acids (PEHP (10) and CHEHP (11), respec-... 

Tryptophan-59 has been modified by formylation, with the formyl group replacing the NH proton on the indole ring, and oxidation with V-bromosuccinimide (NBS). In both cases the hydrogen bond to the buried heme propionic acid is broken, and the molecule undergoes the change in properties outlined in Table XV. Reductase activity is impaired, and the oxidase reaction is also affected somewhat The reaction is slower for any given cytochrome c concentration short of saturation, but the Vm x is the same as for unmodified cytochrome c. The NBS story... 

The four acetic acid side chains are decarboxylated (by the enzyme uro gen decarboxylase) to methyl groups to give copro gen III, followed by the oxidative decarboxylation of the two propionic acid side chains on rings A and B to vinyl groups (via the enzyme copro gen oxidase) giving proto gen IX. Oxidation of proto gen IX to protoporphyrin IX is then accomplished by the enzyme proto gen oxidase, followed by iron insertion catalysed by a very similar enzyme called ferrochelataseF Both enzymes are bound to the inner mitochondrial membrane. 

The reaction of a tryptophan derivative, N- tert-butoxycarbonyl)-L-tryptophan, with hypoxanthine/ xanthine oxidase/Fe(III)-EDTA mainly resulted in the oxygenation of the pyrrole ring of the indole nucleus (Itakura etal. 1994). 2-[(ferf-Butoxy-carbonyl)-amino]-3-(3-indolyl)propionic acid and N- (fer f-butoxycarb onyl) -hT-formylkynurenine were identified as the major products. 

The chemistry of cytochrome oxidase is not well known. From its spectrum the prosthetic group isolated by Negelein is similar to that of a hemin from the snail, Spirographis. This compound contains the structure l,3,5,8-tetramethyl-2-formyl-4-vinylporphin-6,7-propionic acid. A very similar compound has been crystallized recently from horse heart muscle, but its precise structure is not yet established. A green protein isolated from bile salt-solubilized particles has been... 

The limit of aerotolerance of propionic acid bacteria is reached (Shwartz, 1973) when the oxidizing systems NADH oxidase, L-lactate dehydrogenase and superoxide dismutase are inactivated by the soluble oxygen accumulated in die medium. 

Other oxidase inhibitors, such as CO and NaNs, only slightly affected the respiratory activity of the cultures (Bonarceva et al., 1973a, b). The data mentioned above show that propionic acid bacteria do not have a typical cytochrome oxidase sensitive to CO and KCN. The peculiarity of the propionibacterial respiration is also expressed (Chaix and Fromageot, 1939) in that it is stimulated by H2S, similar to chloreUa, but unlike the respiration of other microorganisms. 

The enzymes SOD, catalase and peroxidase are components of the antioxidative defense of the cell. As follows from the above, the CN-resistant respiration of propionic acid bacteria is responsible for most of the oxygen consumed by the cell with the attendant production of H2O2. The same type of respiration is the main source of superoxide radicals. It was shown (Vorobjeva and Kraeva, 1982) that NADH oxidation by membrane fractions of three strains, representing three different species, is accompanied by the formation of superoxide radicals (Table 3.11). Succinate oxidation, however, was not accompanied by a noticeable production of radicals. The highest rate of superoxide production was found in P, globosum, followed by P. coccoides and P. shermanii. Antimycin inhibited NADH oxidase activity in all the strains and simultaneously increased superoxide production by 32, 36 and 15%, respectively, in P. shermanii, P. globosum and P. coccoides. This showed that superoxide radical formation by propionic acid bacteria occurs in that part of the respiration chain that precedes the site of antimycin action. 

Table 3.11. NADH oxidase activity and NADH-dependent superoxide radical generation in propionic acid bacteria...

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