Open AccessCharacterization of two 3‐ketothiolases possessing differing substrate specificities in the polyhydroxyalkanoate synthesizing organism Alcaligenes eutrophus
Author(s) -
Haywood G.W.,
Anderson A.J.,
Chu L.,
Dawes E.A.
Publication year - 1988
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1988.tb02577.x
Subject(s) - polyhydroxyalkanoates , alcaligenes , organism , substrate (aquarium) , substrate specificity , chemistry , bacteria , biology , stereochemistry , biochemistry , enzyme , genetics , ecology , pseudomonas
Two constitutive acetyl‐CoA acetyltransferases (3‐ketothiolases A and B) were purified from Alcaligenes eutrophus . Enzyme A was active with only acetoacetyl‐CoA and 3‐ketopentanoyl‐CoA, whereas enzyme B was active with all the 3‐ketoacyl‐CoAs (C 4 −C 10 ) tested. Enzyme A appeared to be a tetramer ( M r 70 000) with identical subunits ( M r 44 000) and enzyme B had a similar M r of 168 000 (containing M r 46 000 subunits). Enzymes A and B had isoelectric points of 5.0 and 6.4, respectively. The stoichiometry of the reactions catalysed by each enzyme was confirmed. K m values of 44 μM and 394 μM for acetoacetyl‐CoA, and 16 μM and 93 μM for CoA, were determined with enzymes A and B, respectively. Enzymes A and B gave K m values of 1.1 mM and 230 μM, respectively, for acetyl‐CoA. The condensation reaction was potently inhibited by CoA in both cases.