The E-NTPase and PDNPase are two novel and unrelated ectonucleotidase families that have wide substrate specificity, as well as tissue and cell distribution. Members of the E-NTPase family hydrolyse either nucleoside 5'-triphosphates or both diphosphates and nucleoside 5'-triphosphates. Members of the PDNPase family, on the other hand, hydrolyse pyrophosphate bonds of nucleotides and nucleotide sugars and phosphodiester bonds of nucleotides and nucleic acids.
Ascorbate is an essential enzyme cofactor but is often also regarded as an important antioxidant in vivo, protecting against cancer by scavenging DNA-damaging reactive oxygen species. Recent studies suggest that ascorbate sometimes increases DNA damage in humans. Although there is no evidence that any of these effects are deleterious to humans, we might need to change our thinking about the mechanisms of the antioxidant action of ascorbate in vivo. Copyright (C) 1999 Elsevier Science Ltd.
Gamma-hydroxybutyric acid (GHB) is a substance that can be found in the brain cells of mammals. Synthesized from GABA, it is believed to act as a central neuromodulator and has been employed as an anaesthetic, as a treatment for sleep disorders and as a therapeutic agent for managing opioid and alcohol dependence. GHB intake, however, can lead to severe intoxication and repeated use can induce dependence in people with a history of addiction. Other effects of GHB are reported, including its effect on neurotransmitter systems and its interaction with GABA neurotransmission.