4-Maleylacetoacetate (4-maleylacetoacetatic acid) is an intermediate in the metabolism of

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is ...

. It is converted to

fumarylacetoacetate Fumarylacetoacetic acid (fumarylacetoacetate) is an intermediate in the metabolism of tyrosine. It is formed through the conversion of maleylacetoacetate into fumarylacetoacetate by the enzyme maleylacetoacetate isomerase. See also * Fumarylac ...

by the

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

4-maleylacetoacetate cis-trans-isomerase In enzymology, maleylacetoacetate isomerase () is an enzyme that catalysis, catalyzes the chemical reaction :4-maleylacetoacetate \rightleftharpoons 4-fumarylacetoacetate This enzyme belongs to the family of isomerases, specifically Cis-trans is ...

. Gluthathione coenzymatically helps in conversion to fumarylacetoacetic acid.