An open reading frame of the hyperthermophilic archaeon Aeropyrum pernix K-1 APE2325, which composed of 474 bases, was cloned and expressed in Escherichia coli BL21 (DE3) Codon Plus-RIL. The recombinant protein was purified by Ni-chelation affinity chromatography. It showed a single band with a molecular mass of 18 kDa in SDS-PAGE. The purified enzyme exhibited both phospholipase A(2) and esterase activities with the optimal catalytic temperature at 90degreesC. The enzyme activity was Ca2+-independent. Kinetic analysis revealed its K-m, k(cat), and V-m for the p-nitrophenyl propionate substrate were 103 muM, 39 s(-1), and 249 mumol/min/mg, respectively. The recombinant protein was thermostable and its half-life at 100 degreesC was about I h. (C) 2004 Elsevier Inc. All rights reserved.