Characterization of microsomal diacylglycerol acyltransferase activity from bovine adipose and muscle tissue

The activity of the triacylglycerol bioassembly enzyme, diacylglycerol acyl transferase (DGAT), was characterized in microsomal fractions prepared from bovine subcutaneous (SO adipose, intramuscular (IM) adipose, and muscle (p ars costalis diaphragmatis) tissue. The activity of DGAT was generally high er from SC adipose tissue than from IM adipose or muscle tissue. The charac teristics of DGAT activity from the three bovine tissues resembled the acti vity characteristics observed in previous studies from various other organi sms and tissues; the pH optimum was near neutrality, the activity was almos t completely inhibited by pre-incubation with N-ethylmaleimide (NEW and the enzyme accepted a broad range of acyl-CoAs and sn-1,2-diacyiglycerols. In some aspects, the SC adipose tissue DGAT activity was different from the DG AT activity from the other two tissues. The SC adipose tissue DGAT activity was not as susceptible to inhibition by NEM as the enzymes from the two ot her tissue sources, and it exhibited increased specificity for substrates c ontaining oleoyl moieties. The differences in DGAT properties between the t hree bovine tissues may account to some extent for the differences in the r elative fatty acid composition and the positional distribution of fatty aci ds in triacylglycerol between bovine tissues. The observed differences in e nzymatic properties also support recent biochemical and molecular genetic o bservations that imply the existence of multiple DGAT genes and/or isoforms . (C) 2001 Elsevier Science Inc. All rights reserved.