Inhibition of lipoprotein lipase by benzene boronic acid. Effect of apolipoprotein C-II.

The catalytic mechanism of triacylglycerol hydrolysis by lipoprotein lipase was studied. We found lipoprotein lipase to be inhibited by benzene boronic acid, with an apparent Ki of 8.9 micro M at pH 7.4. This indicates the presence of serine and histidine in the active site of the enzyme. Inhibition of lipoprotein lipase by benzene boronic acid is likely to be due to the formation of an inhibitor-enzyme complex having analogous bonding to the active site histidine and serine as the transition-state complex which precedes the formation of an obligatory acyl-enzyme intermediate. The presence of apolipoprotein C-II, the apolipoprotein activator of lipoprotein lipase, partly reverses the inhibition of lipoprotein lipase by benzene boronic acid. This reversal by apolipoprotein C-II has a distinct pH optimum in the range of 8-9.