| Abstract: | A deacetylase-thiolesterase that cleaves both the amide and thiolester bonds of 4-acetamidobutyryl CoA has been highly purified from extracts of Pseudomonas B4 grown in a medium containing L-beta-lysine (3,6-diaminohexanoate) as the main energy source. The enzyme has a molecular weight of about 275,000 and contains 8 apparently identical subunits of 36,500 daltons. Products of 4-acetamidobutyryl CoA degradation are stoichiometric amounts of CoASH and acetate, variable amounts of 4-aminobutyrate and its lactam, 2-pyrrolidinone, and a little 4-acetamidobutyrate. The relative yields of 4-aminobutyrate and 2-pyrrolidinone are determined by the enzyme level. At high enzyme levels the 4-aminobutyrate/pyrrolidinone ratio is about 2, whereas at low enzyme levels only pyrrolidinone is formed. Under the latter conditions, 4-aminobutyryl CoA accumulates transiently and is converted nonenzymatically to pyrrolidinone and CoASH. Since the enzyme does not form 4-aminobutyrate from synthetic or enzymatically formed 4-aminobutyryl CoA, we conclude that a 4-aminobutyryl CoA-enzyme complex is the actual precursor of 4-aminobutyrate, whereas free 4-aminobutyryl CoA is the precursor of pyrrolidinone. Several analogs of 4-acetamidobutyryl CoA containing different amino acid or amide moieties, and several simple acyl CoA compounds are utilized by the enzyme; 4-propionamidobutyryl CoA and 5-acetamidovaleryl CoA are most readily decomposed. Acetyl CoA is a very poor substrate. 3-Acetamidopropionyl CoA is first converted to acetate and beta-alanyl CoA and the latter compound is slowly hydrolyzed to beta-alanine and CoASH. Little deacetylase-thiolesterase is formed by bacteria grown in absence of beta-lysine, but another thiolesterase, lacking deacetylase activity, is produced. The deacetylase-thiolesterase catalyzes an essential step in the aerobic degradation of L-beta-lysine. |
