Camitine synthesis

The food industry is a fertile area for biocatalysis applications high-fructose corn syrup (HFCS) from glucose with glucose isomerase, the thermolysin-catalyzed synthesis of the artificial sweetener Aspartame , hydrolysis of lactose for lactose-intolerant consumers, and the synthesis of the nutraceutical i-camitine in a two-enzyme system from "ybutyrobetaine all serve as examples. 

B-N Zhou, AS Gopalin, F VanMiddlesworth, W-R Shieh, CJ Sih. Stereochemical control of yeast reductions. 1. Asymmetric synthesis ofL-camitine. J Am Chem Soc 105 5925-5926, 1983. 

Even though AMP, not cAMP, may be the protein kinase activator, glucagon causes its activation and insulin, inactivation. Details on such hormone effects are lacking. Also recall that malonyl-CoA inhibits palmitoyl-CoA-camitine acyltrans ferase, the rate-controlling enzyme in the /3-oxidation process. Thus, lipid oxidation is inhibited in an environment that favors lipid synthesis, as in the fed state, whereas lipid biosynthesis is inhibited in an environment favoring lipid oxidation, as in fasting. 

Enzymatic reduction, oxidation, ligase, or lyase reactions, especially, provide us with numerous examples in which prochiral precursor molecules are stereo-selectively functionalized. Ajinomoto s S-tyrosinase-catalyzed L-dopa process [112], the formation of L-camitine from butyro- or crotonobetaine invented by Lonza [113], and the IBIS naproxen route oxidizing an isopropylnaphthalene to an (S)-2-arylpropionic acid are representative, classic examples for many successful applications of enzymatic asymmetric synthesis on an industrial scale. A selection of recent industrial contributions in this field are summarized below. 

In muscle, most of the fatty acids undergoing beta oxidation are completely oxidized to C02 and water. In liver, however, there is another major fate for fatty acids this is the formation of ketone bodies, namely acetoacetate and b-hydroxybutyrate. The fatty acids must be transported into the mitochondrion for normal beta oxidation. This may be a limiting factor for beta oxidation in many tissues and ketone-body formation in the liver. The extramitochondrial fatty-acyl portion of fatty-acyl CoA can be transferred across the outer mitochondrial membrane to carnitine by carnitine palmitoyltransferase I (CPTI). This enzyme is located on the inner side of the outer mitochondrial membrane. The acylcarnitine is now located in mitochondrial intermembrane space. The fatty-acid portion of acylcarnitine is then transported across the inner mitochondrial membrane to coenzyme A to form fatty-acyl CoA in the mitochondrial matrix. This translocation is catalyzed by carnitine palmitoyltransferase II (CPTII Fig. 14.1), located on the inner side of the inner membrane. This later translocation is also facilitated by camitine-acylcamitine translocase, located in the inner mitochondrial membrane. The CPTI is inhibited by malonyl CoA, an intermediate of fatty-acid synthesis (see Chapter 15). This inhibition occurs in all tissues that oxidize fatty acids. The level of malonyl CoA varies among tissues and with various nutritional and hormonal conditions. The sensitivity of CPTI to malonyl CoA also varies among tissues and with nutritional and hormonal conditions, even within a given tissue. Thus, fatty-acid oxidation may be controlled by the activity and relative inhibition of CPTI. 

Fig. 9. Reciprocal regulation of fatty acid synthesis and oxidation. Malonyl-CoA, the product of the ACC reaction, inhibits CPT-1, which is localized at the outer mitochondrial membrane and catalyzes the conversion of fatty acyl-CoA to fatty acyl-camitine for mitochondrial fatty acid import and oxidation. At the inner mitochondrial membrane, fatty acyl moieties are converted to CoA thioesters by CPT-II before undergoing -oxidation. ACC is activated by citrate and inhibited by fatty acyl-CoA. AMPK is activated by AMP and the high AMP level reflects the low energy state of the cell. Activation of AMPK in response to increases in AMP involves phosphorylation by an upstream AMPK kinase (AMPKK), the tumor suppressor LKB1, and AMPK is inactivated/dephosphory-lated by protein phosphatase 2A (PP2A), which is first activated by insulin via PI3K/Akt pathway. ACC is dephosphorylated/activated by PP2A and is inactivated upon phosphorylation by AMPK. ACC can also be phos-phorylated/inactivated by PKA. TAG, triacylglycerol FA, fatty acid.

Tosylation of benzyl ester 45c affords the 4-tosyloxy alcohol 61. Displacement of the tosylate group with trimethylamine followed by hydrogenolysis of the benzyl ester furnishes ( S)-camitine (64) [46]. Attempted synthesis of 64 via the methyl ester 45a fails at the hydrolysis step (leading to 63), which proves to be sluggish. The enantiomeric (/ )-camitine can be synthesized by an identical sequence of reactions starting from (R)-ma ic acid (Scheme 7). 

K. Bock, I. Lundt, and C. Pedersen, Synthesis of S- and R-4-amino-3-hydroxybutyric acid (GABOB) and S- and R-camitine from arabinose or ascorbic acid, Acta Chem. Scand, B37 (1983) 341-344. 

L-carnitine supplementation is routinely provided to patients with GA-1 as a way to reduce intramitochondrial glutaryl-CoA and provide extracellular release without the synthesis of glutaric acid and 3-hydroxyglutaric acid. L-camitine conjugates with coenzyme A esters to form acylcarnitines. The typical L-carnitine dose is 75-100 mg/kg/day or sufficient quantities to maintain free L-camitine concentrations within the normal range [4], Large doses of enteral L-carnitine may cause loose stools or diarrhea [11], In the hospitalized patient with acute illness, a continuous infusion of intravenous L-carnitine is preferably provided. 

Section 6.4.4), both in the nature of the reaction [which requires a lyase to add water (rather than ammonia) across a carbon-carbon double bond] and in the use of growing cells. Purified fumarate hydrolyase is used to manufacture some 500 tonnes of L-(S)-malate (43) each year, while maleic hydrolyases will catalyse the synthesis of D-(/ )-malate (44), a product for which there is as yet no substantial market. Such reactions are also important in the synthesis of both L-camitine (45) and captopril (46) (Scheme 6.21). 

Synthesis of acetyl-L-camitine labeled either in position 1 (route 1 ) or 2 (route 2 ) in the acetyl group... 

Asymmetric synthesis can also sometimes be done by biocatalysis. This has been used in large-scale syntheses for years. For example, the Reich-stein process for the synthesis of vitamin C, established in 1933 and still in use, involves the biotransformation of sorbitol to L-sorbose [41]. L-camitine is used as a thyroid inhibitor. It is prepared by enzymatic hydroxylation of 4-butyrobetaine [42]. 

Upon comparing mitochondria from young and old rats, we did not detect any significant difference between them in their capacity to oxidise substrate, irrespeetive of the substrate used Indeed, in skeletal muscle mitochondria from old rats, there was never an inhibition of state 3 respiration (coupled respiration in which the synthesis and export of ATP is at the maximal rate), whether it was detected using FAD-linked substrate (i.e. succinate+rotenone) orNADH-linked substrate (glutamate + malate and pyruvate + malate) (Lombardi et cd., 2009 Kemer et al., 2001). In addition, we did not observe a difference (old vs. young) in the maximal eapaeity of mitochondria to oxidize lipid whether pahnitoyl-camitine or palmitoyl CoA+ eamitine was used as substrate. 

Desymmetrization of S-hydroxyglutaronitrile 17 toward (l9-4-cyano-3-hydroxybutyric acid 18, a key intermediate in the synthesis of Atorvastalin 19, L-Camitine 20 and (/ )-4-amino-3-hydroxybutyric acid (GABOB, 21) [29,30. ... 

There are only a few examples for the transformations of phosphorus-containing compounds witii baker s yeast [475, 476]. Thus baker s yeast has been used for the synthesis of a-aminophosphonates in a one-pot reaction from aldehyde, diethyl phosphite, and an amine [477]. The reduction of (3-chloro-2-oxo-propyl)-phosphonic acid diethyl ester by baker s yeast gave (2R)-3-chloro-2-hydrox5qjropyl-phosphoric acid diethyl ester, which could be used for the synthesis of (R)-camitine [478-480]. The... 

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