Hydrogen sulphide may also develop under
anaerobic conditions as a result of putrefaction of
sulphur containing amino acids such as cysteine or
methionine (Chou; 2003; EPA, 2003; Li et al., 2009).
Mammals can produce hydrogen sulphide through a
number of different pathways (Fig. 4). According to
Kamoun (2004) and Li et al. (2009), these pathways are
enzymatically catalyzed by Cystathionine β Synthetase
(CBS), Cystathionine γ Lyase (CSE) or Cysteine
Amino Transferase (CAT) Eq. 3-5: