Propionyl oxide

Chemical Designations - Synonyms Methylacetic anhydride Propanoic anhydride Propionyl oxide Chemical Formula (CH3CH2CO)jO. 

Propene Propene Oxide Propene Polymer Propenoic Acid Beta-Propiolactone Propionaldehyde Propionic Acid Propionic Aldehyde Propionic Anhydride Beta-Propionolactone Propionyl Oxide N-Propyl Acetate 2-Propyl Acetate Propyl Alcohol... 

PROPIONIC ANHYDRIDE Methylacetic anhydride, Propanoic anhydride, Propionyl oxide Corrosive Liquid, III 2 2 2 W... 

SYNS METHYLACETIC ANHYDRIDE PROPANOIC ANHYDRIDE PROPIONIC ACID ANHYDRIDE PROPIONYL OXIDE... 

PROPIONYL OXIDE (123-62-6) Combustible liquid (flash point 145°F/63°C). Reacts with water, evolving heat and forming propionic acid. Violent reaction with strong oxidizers, strong acids, caustic materials. Incompatible with ammonia, aliphatic amines, alkanolamines, isocyanates, alkylene oxides, epichlorohydrin, nitromethane. 

Anhydrid kyseliny propionove BRN 0507066 Caswell No. 708 EINECS 204-638-2 EPA Pesticide Chemical Code 077704 HSDB 1215 Methylacetic anhydride Propanoic acid, anhydride Propanoic anhydride Propionic acid anhydride Propionic anhydride Propionyl oxide UN2496. Liquid mp = -45 bp = 170°, bpi8 = 67.5 d = 1.0110 slightly soluble in CCI4, freely soluble in Et20. 

Chemical Designations — Synonyms Acetic acid Propyl ester Methylacetic anhydride Propanoic anhydride Propionyl oxide Chemical Formula CH3COOCH2CH2CH3. Observable Characteristics — Physical State (as normally shipped) Liquid Color Colorless Odor Mild fruity. Physical and Chemical... 

Oxidation of Odd-Carbon Fatty Acids Yields Propionyl-CoA... 

Fatty acids with odd numbers of carbon atoms are rare in mammals, but fairly common in plants and marine organisms. Humans and animals whose diets include these food sources metabolize odd-carbon fatty acids via the /3-oxida-tion pathway. The final product of /3-oxidation in this case is the 3-carbon pro-pionyl-CoA instead of acetyl-CoA. Three specialized enzymes then carry out the reactions that convert propionyl-CoA to succinyl-CoA, a TCA cycle intermediate. (Because propionyl-CoA is a degradation product of methionine, valine, and isoleucine, this sequence of reactions is also important in amino acid catabolism, as we shall see in Chapter 26.) The pathway involves an initial carboxylation at the a-carbon of propionyl-CoA to produce D-methylmalonyl-CoA (Figure 24.19). The reaction is catalyzed by a biotin-dependent enzyme, propionyl-CoA carboxylase. The mechanism involves ATP-driven carboxylation of biotin at Nj, followed by nucleophilic attack by the a-carbanion of propi-onyl-CoA in a stereo-specific manner. 

Succinyl-CoA derived from propionyl-CoA can enter the TCA cycle. Oxidation of succinate to oxaloacetate provides a substrate for glucose synthesis. Thus, although the acetate units produced in /3-oxidation cannot be utilized in glu-coneogenesis by animals, the occasional propionate produced from oxidation of odd-carbon fatty acids can be used for sugar synthesis. Alternatively, succinate introduced to the TCA cycle from odd-carbon fatty acid oxidation may be oxidized to COg. However, all of the 4-carbon intermediates in the TCA cycle are regenerated in the cycle and thus should be viewed as catalytic species. Net consumption of succinyl-CoA thus does not occur directly in the TCA cycle. Rather, the succinyl-CoA generated from /3-oxidation of odd-carbon fatty acids must be converted to pyruvate and then to acetyl-CoA (which is completely oxidized in the TCA cycle). To follow this latter route, succinyl-CoA entering the TCA cycle must be first converted to malate in the usual way, and then transported from the mitochondrial matrix to the cytosol, where it is oxida-... 

FIGURE 24.26 Branched-chain fatty acids are oxidized by o -oxidation, as shown for phytanic acid. The product of the phytanic acid oxidase, pristanic acid, is a suitable substrate for normal /3-oxidation. Isobutyryl-CoA and propionyl-CoA can both be converted to suc-cinyl-CoA, which can enter the TCA cycle. 

Most fatty acids have an even number of carbon atoms, so none are left over after /3-oxidation. Those fatty acids with an odd number of carbon atoms yield the three-carbon propionyl CoA in the final j3-oxidation. Propionyl CoA is then converted to succinate by a multistep radical pathway, and succinate enters the citric acid cycle (Section 29.7). Note that the three-carbon propionyl group should properly be called propnnoyl, but biochemists generally use the non-systematic name. 

Fatty acids with an odd number of carbon atoms are oxidized by the pathway of P-oxidation, producing acetyl-CoA, until a three-carbon (propionyl-CoA) residue remains. This compound is converted to succinyl-CoA, a constiment of the citric acid cycle (Figure 19-2). Hence, the propionyl residue from an odd-chain frtty acid is the only part of a frtty acid that is glucogenic. 

Figure 7.1 The overall pathway of haem biosynthesis. 5-AminolaevuIinate (ALA) is synthesized in the mitochondrion, and is transferred to the cytosol where it is converted to porphobilinogen, four molecules of which condense to form a porphyrin ring. The next three steps involve oxidation of the pyrrole ring substituents to give protoporphyrinogen fX, whose formation is accompanied by its transport back into the mitochondrion. After oxidation to protoporphyrin IX, ferrochelatase inserts Fe2+ to yield haem. A, P, M and V represent, respectively acetyl, propionyl, methyl and vinyl (—CH2=CH2) groups. From Voet and Voet, 1995. Reproduced by permission of John Wiley Sons, Inc.

Oxygen (Gas), Carbon disulfide, Mercury, Anthracene, 4831 Oxygen (Liquid), Carbon, Iron(II) oxide, 4832 Oxygen difluoride, Hexafluoropropene, Oxygen, 4317 Potassium chlorate, Manganese dioxide, 4017 f Propionyl chloride, Diisopropyl ether, 1163 f Propylene oxide, Sodium hydroxide, 1225 Silver azide, 0023 Silver nitride, 0038 Sodium carbonate, 0552 Sodium peroxoborate, 0155 Tetrafluoroammonium tetrafluoroborate, 0133 Triallyl phosphate, 3184... 

The situation is simpler for odd numbered fatty acyl derivatives as [3-oxidation proceeds normally until a 5-carbon unit remains, rather than the usual 4-carbon unit. The C5 moiety is cleaved to yield acetyl-CoA (C2) and propionyl-CoA (C3). Propionyl CoA can be converted to succinyl CoA and enter the TCA cycle so the entire molecule is utilized but with a slight reduction in ATP yield as the opportunity to generate two molecules of NADH by isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase is lost because succinyl-CoA occurs after these steps in the Krebs cycle (Figure 7.18). 

Fatty adds with an odd number of carbon atoms are oxidized by -oxidation identically to even-carbon fiitty acids. The difference results only from the final cyde, in which even-carbon fatty adds yield two acetyl CoA (fiom the 4-carbon ff ment remaining) but odd-carbon fatty adds yield one acetyl CoA and one propionyl CoA (from the 5-carbon fr pnent remaining). 

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. 

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