Leucine biochemical structure

The ability of a tumor cell to manufacture proteins is a result of intact DNA, RNA and biochemical intracellular mechanisms. Interference with any one of these structures or processes will result in the inability of the cell to produce required proteins. Hence, quantitation of tumor cell protein synthesis over a period of time may constitute a marker allowing determination of the efficacy of a macromolecular drug conjugate. The technique is based on the fact that decreased cell viability in the presence of radiolabeled amino adds correlates to a decrease in radioactivity relative to a control cell population. For example, 3H-leucine [175, 208], a mixture of [14C]-labeled amino acids [205], and 75Se-lenomethionine [54, 209] have been used to evaluate the activity of conjugates. 

Branched-chain ketoaciduria (commonly known as Maple Syrup Urine Disease MSUD) is another ailment that may be caused by thiamine deficiency. In MSUD, the oxidative decarboxylation of alpha-keto acids derived from, i.e. valine, isoleucine, and leucine, is blocked due to an inadequate supply of the coenzyme thiamine pyrophosphate (TPP). Clinical symptoms of MSUD include mental and physical retardation. Describe briefly the structure of Riboflavin (Vitamin B-2) and its biochemical role. 

Elastin, a stmctural protein with mbber-like elastic properties. It is the main component of the elastic yellow connective tissue occurring, e.g., in the lungs and aorta. The amount of elastin is rather low in the inelastic white connective tissue of tendons. Elastin consists of 850-870 aa with a high content of Gly (27%), Ala (23%), Val (17%), and Pro (12%). It forms a three-dimensional network of fibers crosslinked by desmosine, lysinonor-leucine, and isodesmosine. It has been reported that elastin has an unanticipated regulatory function during arterial development, controlling the proliferation of smooth muscle and stabilizing arterial structure [L. Robert, W. Hornebeck (Eds.), Elastin and Elastases, Volume 1, CRC Press, Boca Raton, EL, 1989 D. R. Eyre et al, Annu. Rev. Biochem. 1984, 53, 717 D. Y. Li et al., Nature 1998, 393, 276]. 

D. Mastropaolo, A. Camerman, N. Camerman, Crystal structure of leucine-enkephahn, Biochem. Biophys. Res. Commun. 134 (1986) 698-703. 

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