In enzymology, a stizolobate synthase () is an enzyme that catalyzes the chemical reaction 3,4-dihydroxy-L-phenylalanine + O2 4-(L-alanin-3-yl)-2-hydroxy-cis,cis-muconate 6-semialdehyde Thus, the two substrates of this enzyme are 3,4-dihydroxy-L-phenylalanine and O2, whereas its product is 4-(L-alanin-3-yl)-2-hydroxy-cis,cis-muconate 6-semialdehyde. This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O2 as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O2. The systematic name of this enzyme class is 3,4-dihydroxy-L-phenylalanine:oxygen 4,5-oxidoreductase (recyclizing). This enzyme participates in tyrosine metabolism. It employs one cofactor, zinc. References EC 1.13.11 Zinc enzymes Enzymes of unknown structure