Possible Interaction: Cysteine and Methionine

“Furthermore, the total plasma levels of homocysteine were higher, whereas those of cysteine were lower, after methionine loading in both groups.”

“ Blood methionine , homocysteine, and GSSG concentrations were significantly increased when cats consumed the high cysteine content diet but not when they consumed the moderate cysteine content diet, compared with concentrations obtained when cats consumed the nominal cysteine content diet.”

“Factors influencing the utilization of methionine and cysteine , especially those conditions that lead to toxicity on the one hand or beneficial effects on the other, are discussed.”

“Similarly, L-cysteine has a sparing effect on L-methionine when fed to mice; however, D-cysteine does not.”

“Although the methionine dose used was supraphysiologic, these data suggest that an altered tCys response to ingested methionine occurs in obesity, whereby tCys might rise in response to dietary methionine.”

“ Methionine loading decreased tCys from mean 275 (95% CI, 273, 277) μmol/L to 253 (251,255) μmol/L. The decline in tCys was less in overweight (-8%) and obese (-6%) compared to normal weight (-9%) subjects, adjusting for age, gender and CVD (P-ANOVA =0.006).”

“The addition of cysteine to parenteral nutrition (PN) allows for the reduction of the amount of methionine in PN, thereby limiting hepatotoxicity, and acidifies the solution, thereby increasing calcium and phosphate solubility, and potentially improving bone mineralization.”

“Cystathionine beta-synthase (CBS) catalyzes the condensation of serine with homocysteine to form cystathionine and occupies a crucial regulatory position between the methionine cycle and the biosynthesis of cysteine by transsulfuration.”

“Substitution of cysteine 93 with A or M leads to a slight decrease of the rate of beta chain heme release, whereas the obvserved K2,4 value is similar to that obtained for HbA-wt.”

“The results showed that the ratio of methionine to whole free amino acids was significantly higher than that of cysteine.”

“Plasma metabolomics results indicated that the higher ratios of methionine and cysteine (0.51% Met, 0.56% Met, and 0.62% Met)–supplemented groups enriched the level of hippuric acid, retinoic acid, riboflavin, and δ-tocopherol than in the 46% Met group.”