Studies on Lichen Enzymes

Orsellinate decarboxylase, catalyzing the decarboxylation of orsellinic acid (2,4‐dihydroxy‐6‐methyl benzoic acid) to orcinol has been isolated from the lichen Lasallia ptulata. The substrate specificity of the enzyme has been tested: only orsellinic acid, 3‐chloro‐, 5‐chloro‐orsellinic acids, homo‐orsellinic acid (2,4‐dihydroxy‐6‐ethyl benzoic acid) and everninic acid (4‐methoxy‐2‐hydroxy‐6‐methyl benzoic acid) were decarboxylated. The obtained degree of purification was 400‐fold with a hal specific activity of 14.1 units/mg of protein. The purified enzyme has a molecular weight of about 72000 (±10%) as determined by dodecyl sulphate‐polyacrylamide gel electrophoresis. The Kmfor orsellinic acid has been determined as 211 μM, the Ki of the inhibitor β‐resorcylic acid (2,4‐dihydroxy benzoic acid) as 800 μM. A spectrophotometric method suitable for the assay of orsellinate decarboxylase is described.