White R H
Biomed Mass Spectrom. 1983 Dec;10(12):660-4. doi: 10.1002/bms.1200101208.
The incorporation of deuterated serine into cysteine during the metabolism of cystine by Escherichia coli was studied in order to determine the extent to which the carbon-sulfur bond(s) of the cystine is cleaved. The results indicate that the major route (approximately 80%) for cystine metabolism consists of a reductive cleavage of the cystine disulfide bond to form cysteine. Evidence is presented which shows that a portion of the remaining cystine is broken down by a pathway(s) which results in cleavage of the carbon-sulfur bond of the cystine. This pathway would be the same as that expected for the beta-elimination of pyruvate from cystine catalysed by the enzyme beta-cystathionase. In addition, a small portion of the resulting cysteine is shown to undergo a reversible dissociation to serine and hydrogen sulfide. Evidence is presented which shows that this dissociation is caused by the enzyme cysteine synthetase [O-acetyl-L-serine acetate-lyase (adding H2S)].
为了确定胱氨酸的碳-硫键被裂解的程度，对大肠杆菌在胱氨酸代谢过程中将氘代丝氨酸掺入半胱氨酸的情况进行了研究。结果表明，胱氨酸代谢的主要途径（约80%）是胱氨酸二硫键的还原裂解以形成半胱氨酸。有证据表明，其余部分胱氨酸通过一种导致胱氨酸碳-硫键裂解的途径被分解。该途径与由β-胱硫醚酶催化从胱氨酸中β-消除丙酮酸所预期的途径相同。此外，结果表明一小部分生成的半胱氨酸会发生可逆解离，生成丝氨酸和硫化氢。有证据表明这种解离是由半胱氨酸合成酶[O-乙酰-L-丝氨酸乙酸裂解酶（加H₂S）]引起的。
