J. Biol. Chem., Vol. 261, Issue 21, 9678-9683, 07, 1986
Isolation of an active-site peptide of lipoprotein lipase from bovine milk and determination of its amino acid sequence
MN Reddy, JM Maraganore, SC Meredith, RL Heinrikson and FJ Kezdy
Lipoprotein lipase from bovine milk reacted stoichiometrically with
diisopropylphosphorofluoridate (DFP), an inactivator of serine esterases,
resulting in the loss of enzymatic activity against triacylglycerols. The
reaction obeyed first-order kinetics with a rate constant of 0.69 h-1. In
order to isolate the peptide containing the diisopropylphosphoryl moiety
(DIP), partially purified lipoprotein lipase was covalently labeled with
[3H]DFP, and the labeled protein was reduced, carboxymethylated, and
further purified to about 90% homogeneity. Cyanogen bromide cleavage
followed by gel filtration yielded a radioactive peptide of 6-8 kDa. This
peptide was succinylated and then digested with Staphylococcus aureus V8
proteinase. From this digest, a peptide containing 0.95 mol of [3H] DIP/mol
of peptide was isolated by gel-permeation chromatography followed by
reverse-phase high performance liquid chromatography. Automated Edman
degradation provided the following sequence:
Ala-Ile-Gly-Ile-His-Trp-Gly-Gly-
(DIP)Ser-Pro-Asn-Gln-Lys-Asn-Gly-Ala-Val-Phe-Ile-Asn-(Ser, Leu)-Glu.
Analysis of the sequence for secondary structure suggests that the reactive
serine of lipoprotein lipase is in a beta-turn, a structure similar to
those of the active sites of most other serine proteinases. Lipoprotein
lipase appears to share this secondary structure with other serine
hydrolases despite significant differences in the primary structure of this
domain.