Catabolism of Cyst(e)ine by Rat Renal Cortical Tubules

Abstract

Both cysteinesulfinate-independent and cysteinesulfinate-dependent pathways are involved in the catabolism of cyst(e)ine by freshly isolated rat renal cortical tubules. Sulfate and thiosulfate were shown to be the major sulfur-containing products that accumulated in incubations of renal tubules with 1 mmol/L or 25 mmol/L [35S]cyst(e)ine. Thiosulfate is an intermediate in the oxidation of the sulfide produced by the cysteinesulfinate-independent catabolism of cyst(e)ine by desulfhydration pathway(s), whereas sulfate is formed both by further oxidation of thiosulfate and by oxidation of the sulfite formed by the cysteinesulfinate-transamination pathway. Incubation of renal tubules with propargylglycine inhibited gamma-cystathionase activity by 85%, and this resulted in a 46% decrease in sulfate production and a 68% decrease in thiosulfate production when the treated renal tubules were incubated with 1 mmol/L [35S]cyst(e)ine. Addition of 25 mmol/L unlabeled cysteinesulfinate to create a diluting/trapping pool for [35S]cysteinesulfinate formed from [35S]cysteine resulted in a 53% decrease in [35S]sulfate production in incubations with 1 mmol/L cysteine. Thus, some cyst(e)ine catabolism probably occurred by a cysteinesulfinate-dependent pathway. No production of taurine or hypotaurine was detected in incubations with cyst(e)ine. Thus, cysteinesulfinate formed from cysteine was further catabolized primarily to sulfate instead of to taurine and hypotaurine. Most cyst(e)ine catabolism by the epithelial cells of the renal tubule probably can be accounted for by two pathways: 1) the beta-cleavage of cystine catalyzed by lambda-cystathionase and 2) the formation and transamination of cysteinesulfinate catalyzed by cysteine dioxygenase and aspartate aminotransferase.

Метаболізм Цистеїну При Експериментальному Гіпер- Та Гіпотиреозі В Щурів

“…Активність γ-ГЦЛ визначали за кількістю неорганічного фосфату, що утворювався при гідролізі АТФ під час взаємодії глутамату із цис-теїном [15]. Активність ЦДО визначали за швид-кістю перетворення цистеїну в цистеїн сульфінову кислоту [16]. Активність СО визначали за швидкістю окиснення сульфіт-аніона [17].…”

The vasodilatory effect of sulfur dioxide via SGC/cGMP/PKG pathway in association with sulfhydryl-dependent dimerization

“…IN THE LAST DECADE, RESEARCH focusing on sulfur-containing amino acid metabolic pathways indicates that L-cysteine as a substrate cannot only generate hydrogen sulfide (H 2 S) through transsulfuration under cystathionine-␥-lyase or cystathionine-␥-synthase catalysis (35), but also endogenously generate sulfur dioxide (SO 2 ) under cysteine dioxygenase oxidation and aspartate aminotransferase (AAT) transamination (32). Recent studies have shown that endogenous SO 2 is generated in cardiovascular tissues, such as vascular endothelium, medial smooth muscles, right ventricle, and left ventricle (8).…”

Developing high-throughput methods for C. elegans to better understand the newly discovered gasotransmitter sulfur dioxide

“…The toxic gas sulfur dioxide has also been shown to be endogenously generated, via the metabolism of sulfur containing amino acids [4], but was also once thought only to be a toxic byproduct. In 2007, sulfur dioxide was also found to induced vasodilation and because of this it was suggested that it is also a gasotransmitter.…”

“…SO 2 is likely to be a signaling molecule as it is produced endogenously from the metabolism of sulfur containing amino acids [4]. Additionally SO 2 has been found to produce biological effects at physiological concentrations [22], such as vasodilation in isolated rat aortic rings [101] and a decrease in blood pressure of male rats [102,103].…”

“…The enzymatic metabolism occurs via catabolism of cysteine [53]. Cysteine catabolism to cysteinesulfinate is dependent upon cysteine dioxygenase (CDO) [4,107]. CDO concentration is regulated by the availability of methionine and cysteine or protein [108].…”