Butyryl CoA

E. coli C. Kluyveri 4-hydroxy-butyryl-CoA dehydrogenase and R. eutropha phaC P(4HB) 4-hydroxybutyric acid and glucose 68... 

Poly(3HB) is synthesized in bacteria from acetyl-CoA by a three-step reaction (Fig. 1). The first enzyme of the pathway, 3-ketothiolase, catalyzes the condensation of two molecules of acetyl-CoA to form acetoacetyl-CoA. Aceto-acetyl-CoA reductase subsequently reduces acetoacetyl-CoA to R-3-hydroxy-butyryl-CoA, which is then polymerized by the PHA synthase to produce poly(3HB). Since acetyl-CoA is present in plant cells in the cytosol, plastid, mitochondrion, and peroxisome, the synthesis of poly(3HB) in plants could, in... 

OH-butyryl-CoA 3-OH-butyryl-CoA deacylase deficiency deacylase Propionic acidemia Propionyl-CoA carboxylase... 

These short-chain fatty acids are acetic, butyric, lactic and propionic acids, also known as volatile fatty acids, VFA. They are produced from fermentation of carbohydrate by microorganisms in the colon and oxidised by colonocytes or hepatocytes (see above and Chapter 4). Butyric acid is activated to produce butyryl-CoA, which is then degraded to acetyl-CoA by P-oxidation acetic acid is converted to acetyl-CoA for complete oxidation. Propionic acid is activated to form propionyl-CoA, which is then converted to succinate (Chapter 8). The fate of the latter is either oxidation or, conversion to glucose, via glu-coneogenesis in the liver. 

AMP, and pyrophosphate (or, diphosphate). Propenoate can also act as the substrate. This enzyme is not identical with acetyl-CoA synthetase or with butyryl-CoA synthetase. 

Methyl 3-hydroxy butyric aciduria 2-Methyl 3-hydroxy butyryl-CoA dehydrogenase... 

Butyrylglycine C4 Butyryl- CoA (FAO) SCAD deficiency Glutaric acidemia type II... 

Butyryl-CoA dehydrogenase formation of long Steyn-Parve and Beinert 19)... 

In the ruminant mammary tissue, it appears that acetate and /3-hydroxybutyrate contribute almost equally as primers for fatty acid synthesis (Palmquist et al. 1969 Smith and McCarthy 1969 Luick and Kameoka 1966). In nonruminant mammary tissue there is a preference for butyryl-CoA over acetyl-CoA as a primer. This preference increases with the length of the fatty acid being synthesized (Lin and Kumar 1972 Smith and Abraham 1971). The primary source of carbons for elongation is malonyl-CoA synthesized from acetate. The acetate is derived from blood acetate or from catabolism of glucose and is activated to acetyl-CoA by the action of acetyl-CoA synthetase and then converted to malonyl-CoA via the action of acetyl-CoA carboxylase (Moore and Christie, 1978). Acetyl-CoA carboxylase requires biotin to function. While this pathway is the primary source of carbons for synthesis of fatty acids, there also appears to be a nonbiotin pathway for synthesis of fatty acids C4, C6, and C8 in ruminant mammary-tissue (Kumar et al. 1965 McCarthy and Smith 1972). This nonmalonyl pathway for short chain fatty acid synthesis may be a reversal of the /3-oxidation pathway (Lin and Kumar 1972). 

Marshall, M. O. and Knudsen, J. 1980. Factors influencing the in vitro activity of diacyl-glycerol acyltransferase from bovine mammary gland and liver towards butyryl-CoA and palmitoyl-CoA. Biochim. Biophys. Acta 617, 393-397. 

The energy of the butyryl-CoA linkage and of one of the acetyl-CoA linkages is conserved and utilized in the initial formation of crotonyl-CoA (Eq. 17-32). That leaves one acetyl-CoA which can be converted via acetyl-P to acetate with formation of ATP. 

Acetyl-CoA is most often the primer or starter piece for fatty acid synthesis, but butyryl-CoA is a better primer for rabbits. Butyryl-CoA arises from acetyl-CoA by a reversal of (3 oxidation, the necessary enzymes occurring in significant amounts in the cytosol.79 If either acetyl-CoA or butyryl-CoA is the starter piece, chain elongation via malonyl-CoA (Fig. 18-12) leads to fatty acids with an even number of carbon... 

In applying mutasynthesis to the production of novel avermectins, the elimination of branched-chain a-keto acid dehydrogenase (BCDH) was targeted. This multienzyme complex is responsible for supplying the 2-methylbutyryl- and iso-butyryl-CoA starter units that initiate natural avermectin biosynthesis [21,29],... 

The DEBS 1-TE multienzyme was purified to 90-95% homogeneity and then used in another series of experiments to establish the extent to which alternative starter units could be used by the polyketide synthase [36], Substantial amounts of lactones were obtained in the presence of acetyl-, n-butyryl-, and isobutyryl-CoA, illustrating that the loading didomain exhibits a relaxed specificity for the starter unit (Fig. 10). The utilization of acetyl-CoA and -butyryl-CoA by DEBS 1 + TE was demonstrated in a cell-free system [39], Additionally, in the absence of the reducing cofactor NADPH, cell-free DEBS 1+TE converted... 

Figure 10 Biosynthesis of triketide lactones in vitro by DEBS 1-TE. Incubation of propionyl-CoA or acetyl-CoA with methylmalonyl-CoA and NADPH in vitro resulted in synthesis of the appropriate lactones. The mini-PKS also accepted the unnatural starter units ra-butyryl-CoA and isobutyryl-CoA.

Figure 17 Design of assays to evaluate decarboxylation of methylmalonyl-CoA catalyzed by DEBS 1-TE. It was anticipated that a decarboxylase activity would incorporate deuterium into the starter unit of propionyl lactone and that such labeling would be visible by GC-MS analysis. As decarboxylation has been reported in the presence of primers other than propionyl-CoA, assays I—III included n-hutyryl-CoA as a starter unit. Assay IV was designed to evaluate the possibility that -butyryl-CoA suppresses decarboxylation. GC-MS analysis gave no evidence for labeling of the side chain in any assay. Therefore, decarboxylation is not a significant reaction of KSt under these conditions.

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