Open AccessMetabolism of Aromatic Compounds by Fungi
Author(s) -
THATCHER David R.,
CAIN Ronald B.
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03797.x
Subject(s) - sedimentation equilibrium , aspergillus niger , chemistry , guanidine , enzyme , stereochemistry , protein subunit , gel electrophoresis , titration , biochemistry , organic chemistry , gene
1 The molecular weight of 3‐carboxy‐ cis‐cis ‐muconate cyclase obtained from Aspergillus niger has been determined under dissociating conditions. Equilibrium sedimentation studies in the presence of 5 M guanidine hydrochloride (0.1% v/v with respect to 2‐mercaptoethanol) and dodecylsulphate‐calibrated polyacrylamide gel electrophoresis suggested a minimum covalent molecular weight of approximately 24000 for the reduced enzyme. 2 Sedimentation equilibrium studies in the presence of a denaturant but in the absence of a reducing agent gave a value of 47000 for the molecular weight. 3 The amino acid and carbohydrate composition of the enzyme was determined and the presence of one thiol per subunit was shown to be available for titration with 5,5′‐dithio‐bis(2‐nitrobenzoic acid). 4 The enzyme was digested with trypsin, and peptide‐mapping experiments confirmed the hypothesis that 3‐carboxy‐ cis‐cis ‐muconate cyclase consists of eight subunits of approximately 24000 molecular weight and identical chemical composition.