Selenotrisulfide as a Metabolic Intermediate in Biological Systems
ABSTRACT
In 1941, Painter showed that the reaction of selenious acid with low mass
thiols (RSH) produced selenotrisulfide in vitro. Later, the reactivity
of glutathione selenotrisulfide (GSSeSG) with thiols of pancreatic ribonuclease
in an acidic medium was characterized by Ganther. Recently, several RSSeSR
species were actually identified in biological systems by modern mass spectrometry.
Due to the reversibility of the thiol exchange reaction, RSSeSR′ is generated
from the reaction of RSSeSR with R′SH, when increasing the molar ratio
of R′SH to RSSeSR. On the basis of these facts, we investigated the molecular
events of the biogenic thiol-associated selenium transfer in the bloodstream,
with particular attention to selenotrisulfide. We demonstrated that the
selenium transfer from red blood cells to hepatocytes involves a relay
mechanism of thiol exchange that occurs between the selenotrisulfide and
thiols (RSSeSR + R′SH → R′SSeSR + R″SH → R′SSeSR″).