The role of sulfhydryl compounds in mammalian melanogenesis: the effect of cysteine glutathione upon tyrosinase the intermediates of the pathway
References further reading may be available for this article. To view references further reading you must purchase this article.
aDpto. Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Murcia, Murcia Spain
Received 5 May 1988.
The effect of cysteine glutathione on mammalian melanogenesis has been studied. It has been shown that their action is mediated by two different mechanisms. (a) The reaction of the thiol groups with dopaquinone after the tyrosinase-catalyzed oxidation of tyrosine dopa. This mechanism leads to the formation of sulfhydryl-dopa conjugates finally sulfur-containing pigments, phaeomelanins instead of eumelanins. This fact might produce an inhibition of melanogenesis due to the slower rate of chemical reactions involved in the polymerization of such thiol-conjugates when compared to that of indoles. (b) The direct interaction between the sulfhydryl compounds the tyrosinase active site. This interaction may regulate the activity of the enzyme. It is shown that Harding-Passey mouse melanoma tyrosinase is more sensitive to sulfhydryl compounds than mushroom tyrosinase. Cysteine always produces an inhibition of the tyrosinase hydroxylase dopa oxidase activities of melanoma tyrosinase, this inhibition becoming greater as the cysteine concentration increases. On the other h, glutathione produces an activation of the tyrosine hydroxylase activity below 3 mM an inhibition at higher concentrations. The limit between the enzymatic activation inhibition appears at glutathione concentrations similar to the physiological levels of this compound found in melanocytes. Although the switch from eumelanogenesis to phaeomelanogenesis occurs at much lower concentrations of glutathione, taking into ac these data it is discussed that this sulfhydryl compound may regulate not only the type but also the amount of melanin formed inside melanocytes.
Keywords: Melanogenesis; Tyrosinase; Cysteine; Glutathione; Phaeomelanin
Abbreviations: BSA, bovine serum albumin; dopa, 3,4-dihydroxyphenylalanine; DTNB, 5,5′-dithiobis(2-nitrobenzoic acid); PMSF, phenylmethylsulfonyl fluoride; dimethyl-POPOP, 1,4-bis-[4-methyl-5-phenyl-2-oxazolyl]benzene, PPO, 2,5-diphenyloxazole
Correspondence: F. Solano, Dpto. Bioquímica y Biología Molecular, Facultad de medicina, Universidad de Murcia, Murcia 30100, Spain.
含巰基化合物在哺乳動物色素形成中的生化角色
半胱氨酸、谷胱甘肽在對鉻氨酸酶形成色素及中間產(chǎn)物的影響
1988,5月 穆爾西亞大學(xué)醫(yī)學(xué)院，穆爾西亞，西班牙
摘要
本文研究半胱氨酸及谷胱甘肽對哺乳動物體內(nèi)中色素產(chǎn)生過程中的影響機(jī)制。影響機(jī)制分為以下兩類：① 半胱氨酸及谷胱甘肽內(nèi)的巰基與鉻氨酸經(jīng)由鉻氨酸酶催化與Dopa合成產(chǎn)生的色素中間體Dopaquinone作用形成巰基Dope，形成另一中間產(chǎn)物。這個作用干擾并阻止真黑色素的形成。② 巰基與鉻氨酸酶上有效催化作用的位置產(chǎn)生化學(xué)作用，因而降低鉻氨酸酶的催化作用，從而降低鉻氨酸轉(zhuǎn)變?yōu)樯氐幕瘜W(xué)作用速度。半胱氨酸及谷胱甘肽兩者都明顯的隨著濃度增加而有效的延緩并阻斷色素種類及數(shù)量的形成。
