Sulfur reduction by human erythrocytes

Abstract

Washed human erythrocytes incubated with glucose and S8 and purged with N2 produced H2S at a nearly constant rate of 170 μmol (L cells)–1 min–1, which continued for several hours. In sealed vials up to 25 mM HS– accumulated. Glucose caused the fastest H2S production, although either lactate or glycerol could support slower rates. When glucose was added without S8, anoxic H2S production nonetheless occurred at about 1.5% of the maximum rate, after 24 hr totaling 0.5 mmol H2S (L cells)–1, suggesting the presence of endogenous reducible sulfur. Anaerobic conditions were not required, since oxygenated cells produced H2S from S8 at 80% of the anoxic rate. Using cell lysates, production of H2S occurred after addition of either glutathione, NADH, or NADPH. The observations suggest possible physiological roles for H2S as an electron carrier, and are consistent with an evolutionary relationship between eukaryotic cytoplasm and sulfur‐reducing Archaea. J. Exp. Zool. 282:310–322, 1998. © 1998 Wiley‐Liss, Inc.

Metabolic integration during the evolutionary origin of mitochondria

“…Human erythrocytes were a particularly interesting cell type because they have no mitochondria. When elemental sulfur was added to human red cells, H 2 S was copiously produced, including even when O 2 was present [49].…”

Key bioactive reaction products of the NO/H2S interaction are S/N-hybrid species, polysulfides, and nitroxyl

“…* This notion is consistent with a number of observations: H 2 S is essential for efficient abiotic amino acid generation as evidenced by the recent reanalysis of samples of Stanley Miller's original spark discharge experiments (4), sulfide is an efficient reductant in protometabolic reactions forming RNA, protein, and lipid precursors (5), and sulfide is both a bacterial and mitochondrial substrate (6), enabling even multicellular lifeforms to exist and reproduce under conditions of permanent anoxia (7). Thus, although eukaryotic cells may have originated from the symbiosis of sulfurreducing and -oxidizing lifeforms within a self-contained sulfur redox metabolome (8), sulfide may have been essential even earlier by providing the basic building blocks of life.…”

The Oxidative Stress of Hyperhomocysteinemia Results from Reduced Bioavailability of Sulfur-Containing Reductants

“…S may either endorse the role of stimulatory factor of several mammalian apoenzyme activities as shown for succinic dehydrogenase [73] and NADHdehydrogenase [74] or operate as inhibitory agent of other mammalian apoenzymes such as adenylate kinase [75] and liver tyrosine aminotransferase [76]. Elemental S resulting from dietary supply or from sulfane-sulfur decay may be subjected to non-enzymatic reduction in the presence of Cys and GSH [25,26] and/or reducing equivalents obtained from glucose oxidation [25], hence yielding at physiological pH additional provision of H 2 S.…”

“…The endogenous production of the naturally occurring H 2 S reductant depends on Cys bioavailability through the mediation of TS enzymes [23,24]. Production of H 2 S may also occur in human tissues starting from elemental sulfur, a non-enzymatic reaction requiring the presence of Cys, GSH, and glucose [25,26]. It would be worth disentangling the respective roles played by Cys, GSH and H 2 S for the prevention and restoration of HHcy-induced oxidative lesions.…”