title: Biocatalytic formation of synthetic melanin: the role of vanadium haloperoxidases, L-DOPA and iodide.
abstract: The vanadium haloperoxidase (V-HPO) enzyme, extracted from the brown alga Laminaria saccharina, is able to catalyze the formation of a black precipitate, using as precursor the amino acid L-dopa in the presence of hydrogen peroxide and iodide, in one-pot synthesis. The L-dopa oxidation is a multistep reaction with a crucial role played by the iodide in the enzyme catalyzed peroxidative production of dopachrome, a well known intermediate in the synthesis of melanin. Dopachrome is then converted to a synthetic form of melanin through a polymerization reaction. Factors, such as buffer composition and pH, influence significantly the reaction first steps, but further steps of melanin production are hardly influenced. The biosynthetic melanin produced through the combination V-HPO/I/H(2)O(2), was characterized by several spectroscopic techniques (UV-vis and FT-IR) as well as XRD. Moreover, this biopolymer is light sensitive, decomposing into oligo- and monomeric units. Scanning electron microscopy (SEM) imaging showed different morphologies when compared with commercial available melanin. The biosynthetic production of melanin can have a wide range of applications from photosensitive cells to biomedicine with the advantage of being produced under eco-friendly and mild conditions.
authors.affiliation: Centro de Química e Bioquímica do Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: Marisa
authors.initials: M
authors.lastname: Nicolai
authors.forename: Gisela
authors.initials: G
authors.lastname: Gonçalves
authors.forename: Filipe
authors.initials: F
authors.lastname: Natalio
authors.forename: Madalena
authors.initials: M
authors.lastname: Humanes
mesh_terms: D055162:Biocatalysis; D002021:Buffers; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D045563:Indolequinones / Q000737:chemistry / Q000378:metabolism; D007454:Iodides / Q000737:chemistry; D007700:Kinetics; D007980:Levodopa / Q000737:chemistry / Q000378:metabolism*; D008543:Melanins / Q000096:biosynthesis* / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D010544:Peroxidases / Q000378:metabolism*; D058105:Polymerization; D011487:Protein Conformation; D014639:Vanadium / Q000737:chemistry*
chemical_list: D002021:Buffers; D045563:Indolequinones; D007454:Iodides; D008543:Melanins; D014639:Vanadium; C001123:dopachrome; D007980:Levodopa; D006861:Hydrogen Peroxide; D010544:Peroxidases