Growing evidence has demonstrated that, as an endogenous signaling gasotransmitter, hydrogen sulfide (H(2)S) plays an important role in regulating numerous biological functions. The role of H(2)S in hypoxia-induced radioresistance on hepatoma cells was investigated in the present work. Results showed that, when HepG2 cells were maintained in hypoxia circumstances for 4 h, the cellular radioresi...

Hydrogen sulfide (H2S) is an endothelium-derived hyperpolarizing factor that enhances the relaxation of the peripheral vasculature,1–3 recent studies4–6 have also reported its physiological functions in the central nervous system. In mammalian tissues, H2S is produced through degradation of l-cysteine mainly by 2 main enzymes: cystathionineβ-synthase (CBS) and cystathionine-γ-lyase. CBS is prim...

Homocysteine can be methylated to form methionine by the cobalamin- (Cbl) and folate-dependent enzyme, methionine synthase; serum levels of total homocysteine are elevated in greater than 95% of patients with either Cbl or folate deficiency. Homocysteine can also condense with serine to form cystathionine in a pyridoxal phosphate-dependent reaction catalyzed by cystathionine beta-synthase. Cyst...

We investigated the effect of pyridoxine administration in three patients with homocystinuria due to cystathionine synthase deficiency. The drug decreased the plasma concentration and urinary excretion of methionine and homocystine and the urinary excretion of homolanthionine and the homocysteine-cysteine mixed disulfide. Urinary cystine rose somewhat. Oral methionine tolerance tests before and...