Open AccessThe Threonine‐Sensitive Homoserine Dehydrogenase and Aspartokinase Activities of Escherichia coli K‐12
Author(s) -
JACQUES Yannick,
TRUFFABACHI Paolo
Publication year - 1976
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1976.tb10182.x
Subject(s) - homoserine , threonine , dithiothreitol , dimer , chemistry , biochemistry , enzyme , escherichia coli , dissociation (chemistry) , stereochemistry , serine , organic chemistry , virulence , gene , quorum sensing
Aspartokinase I–homoserine dehydrogenase I from Escherichia coli K‐12, a homotetrameric enzyme, dissociates into dimers upon alkaline treatment. Both aspartokinase and homoserine dehydrogenase inactivation, as well as desensitization towards l ‐threonine, occur in a multi‐step process. Dithiothreitol stabilizes a dimeric form retaining full activity and sensitivity; l ‐homoserine stabilizing another dimeric form devoid of aspartokinase activity and retaining a substantial dehydrogenase activity insensitive towards l ‐threonine. A model is proposed showing that dissociation into dimers occurs in a first step, the resulting dimer losing both aspartokinase and homoserine dehydrogenase sensitivity in two subsequent steps involving the formation of intrachain disulfide bonds.