Biotin glucose metabolism

Albarracin CA, Fuqua BC, Evans JL, and Goldfine ID. Chromium picolinate and biotin combination improves glucose metabolism in treated, uncontrolled overweight to obese patients with type II diabetes. Diabetes Metab. Res. Rev. 24 41-51 (2008). 

To replace losses, oxaloacetate can be synthesized from pyruvate and C02 in a reaction that uses ATP as an energy source. This is indicated by the heavy gray line leading downward to the right from pyruvate in Fig. 10-1 and at the top center of Fig. 10-6. This reaction depends upon yet another coenzyme, a bound form of the vitamin biotin. Pyruvate is formed from breakdown of carbohydrates such as glucose, and the need for oxaloacetate in the citric acid cycle makes the oxidation of fats in the human body dependent on the concurrent metabolism of carbohydrates. 

Shiio I, Otsuka S, Katsu N. Effect of biotin on the bacterial formation of glutamic acid. II. Metabolism of glucose.J Biochem 1962 52 108-16. 

Biotin acts as a prosthetic group of carboxylases involved in the metabolism of fatty acids, amino acids and glucose. 

Fig. 13.5 Comparison of metabolic flux redistributions at the 2-oxoglutarate branch between C glutamicum and C. efficiens in glutamate overproduction under biotin limitation and Tween 40 addition. Glucose was used as a carbon source in this experiment. Input flux to 2-oxoglutarate from isocitrate was normalized to 100, and redistributed fluxes to succinyl-CoA and glutamate from 2-oxoglutarate are shown...

Furthermore, adequate minerals and vitamins must Ere available for the proper metabolism of glucose. Minerals are cofactors with many of the enzymes involved, and with the B complex vitamins—thiamin, niacin, ribroflavin, pantothenic acid, vitamin B-6, biotin, and folacin. 

It is not yet clear whether biotin is a cofactor no biotin was detected in highly purified preparations of the enzyme. Malate easily converts to oxaloacetate. The formation of oxaloacetate by one of these two pathways is significant, because it provides the initial spark for the citrate cycle, since oxaloacetate is needed as partner for the condensation reaction with acetyl-CoA. Furthermore, oxaloacetate mediates the resynthesis of glucose (see below). It should be pointed out, finally, that pyruvate can be transformed to alanine (Chapt. VIII-10) by transamination so that pyruvate also represents a link to the metabolism of protein. 

Several of the B vitamins are essential for normal fatty-acid metabolism (Table 2). Pantothenic acid is a constituent of CoA and is thus required for numerous reactions of fatty acids. Niacin and riboflavin are necessary for the synthesis of oxidized and reduced NAD(P) and FAD, respectively. These compounds play essential roles in fatty-acid oxidation, synthesis, and elongation. Biotin is a constituent of acetyl-CoA carboxylase and pyruvate carboxylase, both of which are involved in the synthesis of fatty acids from glucose. Thiamine is required for activity of the pyruvate dehydrogenase complex, which also participates in fatty-acid synthesis from glucose. 

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