Open AccessSome Properties of d-Mannose Isomerase from Escherichia coli K12
Author(s) -
Fred J. Stevens,
Priscilla Wilkins Stevens,
J. G. Hovis,
Tai Te Wu
Publication year - 1981
Publication title -
microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.352
H-Index - 35
eISSN - 1465-2080
pISSN - 1350-0872
DOI - 10.1099/00221287-124-1-219
Subject(s) - tetramer , mannose , escherichia coli , enzyme , strain (injury) , isomerase , mutant , biochemistry , dimer , catabolism , chemistry , xylose isomerase , xylose , biology , stereochemistry , gene , fermentation , organic chemistry , anatomy
A second-stage mutant of Escherichia coli K12 designated as strain 806 grew faster on D-lyxose than the mutant strain 805 previously described. Both mutants produced constitutively a novel enzyme, D-mannose isomerase, but strain 806 produced twice as much as strain 805. The enzyme could fortuitously convert D-lyxose to D-xylulose, which is a normal intermediate in the D-xylose catabolic pathway. The purified enzyme consisted of four subunits each with a molecular weight of about 40 000. In 0.14 M-Na2SO4, the tetramer dissociated completely into dimers. While the tetramer Km values for D-mannose and D-lyxose were 80 mM and 300 mM, respectively, the dimer Km values for these two sugars were both 300 mM. The amino acid composition of the enzyme was also determined.