HYDROLYSIS AND ALCOHOLYSIS OF ORTHOTHIO ESTERS
HYDROLYSIS AND ALCOHOLYSIS OF ORTHOTHIO ESTERS
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DOI：
10.1002/chin.197440212
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发表时间：
1974-10
期刊：
影响因子：
--
通讯作者：
R. A. Ellison;W. Woessner;C. C. Williams-C.
中科院分区：
文献类型：
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作者：
R. A. Ellison;W. Woessner;C. C. Williams-C.
Spectroscopic Studies of the Oxidation of Tyrosine Peptides with the Cu2+/Hz02 System. As is the case with other oxidizing agents, the effect of theCu2+/H202 system on tyrosine peptides depends on the position of the tyrosine moiety in the peptides. With the NH2-terminal tyrosine peptide, L-tyrosyl-L-leucine (1, R= leucine moiety), the Cu2^/H2Ü2 system gave an absorption spectrum (Figure 2, curves 1, 2, and 3) similar to that found by Dukler, et al., 4 when tyrosylglycylglycine was oxidized by potassium nitrosodisulfonate (maximum at 475 nm). Dukler, et al., have attributed the spectrum to the fact that the N-terminal peptide was oxi-dized by a dopachrome mechanism, forming an amino-chrome; analogously, the present product may be regard-ed as an aminochrome (2, R= leucine moiety). At room temperature and with excess Cu2+/H2C> 2 the amino-chrome absorption at 475 nm increased up to 4 hr, and then slowly began to decline. With neither potassium nitrosodisulfonate nor the present Cu2+/H202 system was treatment with Pt black required for aminochrome forma-tion from NH2-terminal tyrosine peptides. Addition of Pt black produced no significant changes in the spectrum other than reduction of the end absorption at shorter wavelengths.With the COOH-terminal tyrosine peptide DL-leucyl-DL-tyrosine, the absorption spectrum obtained on addition of excess Cu2+/H202 gave no indication of formation of an aminochrome (maxima at 305 and 475 nm) or of an o-qui-none (maximum at 390 nm) after 6 hr at room temperature (Figure 2, curve 4). Similar results were obtained with another COOH-terminal tyrosine peptide, glycyl-L-tyrosine. Even after 14 hr at room temperature, followed by treatment with Pt black, no spectral evidence that the COOH-terminal tyrosine peptides were oxidized by either an aminochrome mechanism or a dopaquinone pattern was obtained. The dopaquinone pattern of oxidation of COOH-terminal tyrosine peptides occurs on enzymatic oxidation2 and on oxidation with potassium nitrosodisul-fonate. 4
