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For example, laccases play a role in the formation of lignin by promoting the oxidative coupling of monolignols, a family of naturally occurring phenols. [1] [2] Other laccases, such as those produced by the fungus Pleurotus ostreatus, play a role in the degradation of lignin, and can therefore be classed as lignin-modifying enzymes. [3]
Lignin-modifying enzymes benefit industry as they can break down lignin; a common waste product of the paper and pulp industry. These enzymes have been used in the refinement of poplar as lignin inhibits the enzymatic hydrolysis of treated poplar and Lignin-modifying enzymes can efficiently degrade the lignin thus fixing this problem. [4]
[1] [5] PAL has recently been studied for possible therapeutic benefits in humans afflicted with phenylketonuria. [6] It has also been used in the generation of L-phenylalanine as precursor of the sweetener aspartame. [7] The enzyme is a member of the ammonia lyase family, which cleaves carbon–nitrogen bonds
Much about its anabolism is not understood even after more than a century of study. [5] Polymerisation of coniferyl alcohol to lignin. The reaction has two alternative routes catalysed by two different oxidative enzymes, peroxidases or oxidases. The polymerisation step, that is a radical-radical coupling, is catalysed by oxidative enzymes.
The net reaction follows the following stoichiometry, illustrated with a generic methoxy arene: [1] ArOCH 3 + O 2 + 2 e − + 2 H + → ArOH + CH 2 O + H 2 O. The enzyme is notable for its promiscuity, affecting the O-demethylation of a range of substrates, including lignin. It is a heterodimeric protein derived from the products of two genes.
Lignin is found to be degraded by enzyme lignin peroxidases produced by some fungi like Phanerochaete chrysosporium. The mechanism by which lignin peroxidase (LiP) interacts with the lignin polymer involves veratrole alcohol , which is a secondary metabolite of white rot fungi that acts as a cofactor for the enzyme.
The systematic name of this enzyme class is Mn(II):hydrogen-peroxide oxidoreductase. Other names in common use include peroxidase-M2, and Mn-dependent (NADH-oxidizing) peroxidase. It employs one cofactor, heme. This enzyme needs Ca 2+ for activity. White rot fungi secrete this enzyme to aid lignin degradation.
The name ficin was first used by Robbins in 1930 to describe a purified substance with anthelmintic activity isolated from any member of the fig genus. [6] The Enzyme Commission of the International Union of Biochemistry and Molecular Biology (IUBMB) originally assigned EC 3.4.4.12 as ficin in 1961, which was transferred to 3.4.22.3 and renamed to ficain in 1972, making the two term synonymous ...