Long chain enzyme-catalyzed reactions

Transition-metal- and enzyme-catalyzed alkylations of ammonia and amines with alcohols and diols have been reviewed59. RuCl2(PPh3)3 is a homogeneous catalyst for the reaction of long-chain terminal alcohols with secondary amines to give tertiary amines (equation 22)60. 

This enzyme [EC 2.3.1.76], also referred to as retinol fatty-acyltransferase, catalyzes the reaction of an acyl-CoA derivative with retinol to generate coenzyme A and the retinyl ester. The CoA derivative can be palmi-toyl-CoA or other long-chain fatty-acyl derivatives of coenzyme A. 

This enzyme [EC 2.5.1.26], also known as alkylglycerone-phosphate synthase, catalyzes the reaction of 1-acylglyc-erone 3-phosphate with a long-chain alcohol to produce 1-alkylglycerone 3-phosphate and a long-chain acid anion. In this reaction, the ester-hnked fatty acid of the substrate is removed and replaced with a long-chain alcohol in an ether hnkage. 

This enzyme [EC 6.2.1.15], also known as arachido-nateiCoA ligase, catalyzes the reaction of arachidonate with ATP and coenzyme A to generate arachidonyl-CoA, AMP, and pyrophosphate (or, diphosphate). The enzyme can also use 8,11,14-icosatrienoate as a substrate, but not the other long-chain fatty acids. It should be noted that this enzyme is not identical to long-chain acyl-CoA synthetase [EC 6.2.1.3]. 

This FMN-dependent enzyme [EC 1.1.3.15], also known as (5)-2-hydroxy-acid oxidase, catalyzes the reaction of a (5)-2-hydroxy acid with dioxygen to produce a 2-oxo acid and hydrogen peroxide. The enzyme exists as two major isoenzymes. The A form of the protein preferentially oxidizes short-chain aliphatic hydroxy acids. The B form preferentially oxidizes long-chain and aromatic hydroxy acids. The rat isoenzyme B form also acts as an L-amino-acid oxidase. 

This enzyme [EC 1.1.1.35] catalyzes the reaction of an (5)-3-hydroxyacyl-CoA with NAD+ to produce a 3-oxo-acyl-CoA and NADH. The enzyme will also utilize 5-3-hydroxyacyl-A-acylthioethanolamine and 5-3-hydroxya-cylhydrolipoate as substrates. The enzyme isolated from some sources can also utilize NADP+ as the coenzyme, albeit as a weaker substrate. In addition, there is a broad specificity with respect to the acyl chain length (note that there is a long-chain-length 3-hydroxyacyl-CoA de-hydogenase [EC 1.1.1.211]). 

This enzyme [EC 1.3.99.13] catalyzes the reaction of a long-chain acyl-CoA with an electron-transferring fla-voprotein to produce a 2,3-dehydroacyl-CoA and the reduced electron-transferring flavoprotein. 

This enzyme [EC 1.2.1.48] catalyzes the reaction of a long-chain aldehyde with NAD to produce a long-chain acid anion and NADH. The best substrate is reported to be dodecylaldehyde. 

This enzyme [EC 1.1.1.73] will catalyze the reaction of 1-octanol with NAD+ to produce 1-octanal and NADH. The enzyme can act on other long-chain alcohols, albeit not as effectively. 

The PDH complex of mammals is strongly inhibited by ATP and by acetyl-CoA and NADH, the products of the reaction catalyzed by the complex (Fig. 16-18). The allosteric inhibition of pyruvate oxidation is greatly enhanced when long-chain fatty acids are available. AMP, CoA, and NAD+, all of which accumulate when too little acetate flows into the citric acid cycle, allosterically activate the PDH complex. Thus, this enzyme activity is turned off when ample fuel is available in the form... 

Very long chain fatty acids are initially oxidized in the peroxisome where the initial oxidation step is catalyzed by acyl-CoA oxidase and the subsequent steps in fS-oxidation are catalyzed by a multi-enzyme complex with hydratase, dehydo-genase, and thiolase activities. Unsaturated fatty acids require additional enzymatic activities, including enoyl-CoA isomerase and dienoyl-CoA reductase. Readers are directed to Vance and Vance (2) for additional details regarding fi-oxidation, including the details of the metabolic reactions. 

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