Hydroxybutyrate Hydroxybutyric acid, degradation

Ohura T, Aoyagi Y, Takagi K, Yoshida Y Kasuya K, Doi Y. Biodegradation of poly (3-hydroxyalkanoic acids) fibers and isolation of poly (3-hydroxybutyric acid)-degrading microorganisms under aquatic environments. Polym Degrad Stab 1999 63 23. 

Poly(orthoesters) represent the first class of bioerodible polymers designed specifically for dmg deUvery appHcations (52). In vivo degradation of the polyorthoester shown, known as the Al amer degradation, yields 1,4-cydohexanedimethanol and 4-hydroxybutyric acid as hydrolysis products (53). 

DIRECT DEGRADATION OF THE BIOPOLYMER POLY[(R)-3-HYDROXYBUTYRIC ACID] TO (R)-3-HYDROXYBUTANOIC ACID AND ITS... 

Degradation procedures analogeus to those used for mycobactin P (see above) showed the aromatic residue to be salicylic acid (2-hydroxy-6-methylbenzoic acid in mycobactin P) and the hydroxy acid to be (+)-( -hydroxybutyric acid ((-)-3-hydroxy-2-methylpentanoic acid in mycobactin P). Fatty acid side chains substantially different from those in mycobactin P a minor component contains a s-octadec-2-enoic acid (identical to the principal product in mycobactin P). The major substituents in the fatty acid side chain are Cis to C21 fragments of unknown constitution. 

During prolonged starvation or when carbohydrate metabolism is severely impaired, as in uncontrolled diabetes mel-iitus (see Chapter 25), the formation of acetyl-CoA exceeds the supply of oxaioacetate. The abundance of acetyl-CoA results from excessive mobilization of fatty acids from adipose tissue and excessive degradation of the fatty acids by p-oxidation in the liver. The resulting acetyl-CoA excess is diverted to an alternative pathway in the mitochondria and forms acetoacetic acid, P-hydroxybutyric acid, and acetone—three compounds known collectively as ketone bodies (Figure 26-9). The presence of ketone bodies is a frequent finding in severe, uncontrolled diabetes melUtus. 

PCL was also degraded to 6-hydroxyhexanoic acid during enzymatic hydrolysis by Lipase Asahi derived from Chromobacterium viscosum and Hp-ase F derived from Rhizopus niveus [74]. In another study formation of oligomers during biotic hydrolysis of PCL was shown by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) [50]. Enzymatic degradation of copolymers of 3-hydroxybutyric acid (3HB) and... 

Under some conditions, fatty acid degradation occurs more rapidly than glycolysis. As a result, a large amount of acetyl CoA is produced from fatty acids, but little oxaloac-etate is generated from pyruvate. When oxaloacetate levels are too low, the excess acetyl CoA is converted to the ketone bodies acetone, acetoacetate, and (3-hydroxybutyrate. 

The first poly(ortho ester) for biomedical applications was produced by Choi and Heller at Alza Corporation in the 1970s, and was given the trade name Alzamer . When placed in an aqueous environment, the polymer degrades to produce a diol and a lactone, which is rapidly converted into y-hydroxybutyric acid ... 

This degradation process is autocatalytic, since the g-hydroxybutyric acid that is produced catalyzes the hydrolysis reaction. To prevent abrupt degradation and erosion, a basic compound must be incorporated into the polymer. For example, sodium bicarbonate can be incorporated into a polymeric device composed of Alzamer to control the rate of polymer degradation and erosion. Although the polymer has been used for a number of drug delivery applications, it is difficult to produce and requires addition of significant amounts of a basic chemical to prevent uncontrolled degradation [21]. 

Abe, H. and Doi, Y B/oraacwmo/e. 2002, 3/7/, 33- 3i. Side-Chain Effect of Second Monomer Units on Crystalline Morphology, Thermal Properties, and Enzymatic Degradability for Random Copolyesters of (R)-3-Hydroxybutyric Acid with (R)-3-Hy-droxyalkanoic Acids. 

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