Purification and properties of a pig heart thiolase with broad chain length specificity and comparison of thiolases from pig heart and Escherichia coli.

摘要: A thiolase (acetyl CoA acyltransferase, EC 2.3-1.16) which acts on substrates of various chain lengths (thiolase I) has been purified from pig heart muscle 366-fold to near homogeneity as judged by gel electrophoresis. Its molecular weight was estimated be 200,000 in the absence and 46,000 presence sodium dodecyl sulfate. Kinetic measurements with acetoacetyl coenzyme A, 3-ketohexanoyl-CoA, 3-ketooctanoyl-CoA, 3-ketodecanoyl-CoA yielded apparent Km values 16, 8.3, 2.4, 1.8 micron, respectively, whereas Vmax 65 69 mumol/min/mg were obtained all except for acetoacetyl-CoA, a value 26.5 observed. Antibodies prepared against this used demonstrate that I acetoacetyl-CoA thilase II) mitochondria are immunologically unrelated. The antibodies cross-reacted, however, beef heart. constants (Km, Vmax) also determined thiolases II Escherichia coli, native subunit weights E. coli II. Although found distinct enzymes, their physical kinetic properties strikingly similar those thiolases. In view finding known physiological functions thiolases, it is proposed only involved fatty acid metabolism, solely ketone body degradation.