Cysteine is converted into pyruvate and hydrogen sulfide (H2S) through desulphuration and deamination. Then, H2S is oxidised by SQR, after which ETHE1 takes care of converting into sulfite (SO3 2-). One disorder named Ethylmalonic encephalopathy (EE) is linked to this pathway, a rare mitochondrial disease caused by variants within the ETHE1 gene.
This pathway was inspired by Chapter 9 (edition 4) of the book of Blau (ISBN 3642403360 (978-3642403361)).