Isolation and sequence analysis of a cDNA encoding human placental tissue protein 13 (PP13), a new lysophospholipase, homologue of human eosinophil Charcot-Leyden crystal protein

Expression of placental tissue protein 13 (PP13) in different human tissues was investigated by chemiluminescence Western blot analysis using monospec ific anti-PP13 serum. In term placentae we detected a 16 kDa single protein band immunochemically identical to the purified PP13 antigen. After invest igation of 26 types of human fetal and adult tissue, PP13 was also found in certain other normal and tumorous tissue extracts. It is not secreted into circulation as we could not find PP13 in sera of pregnant women. A full le ngth cDNA with 578 bp insert was isolated by screening a human placental cD NA library with anti-PP13 serum. The open reading frame of the cDNA encodes for a 139-residue-long protein with a predicted molecular mass of 16.118 k Da, identical to the previously isolated and characterized PP13 antigen des cribed in 1983. By alignment search of the protein databank PP13 is highly homologous (69 per cent) to the 16.5 kDa human eosinophil Charcot-Leyden Cr ystal protein, a unique dual-function lysophospholipase, a member of the be ta-galactoside binding S-type animal lectin superfamily. Northern blot anal ysis revealed a 600 bp PP13 mRNA, detected only in placental tissue from 16 types of human healthy adult tissue. Lysophospholipase activity of PP13 wa s confirmed by H-1 and P-31 nuclear magnetic resonance (NMR) measurements. (C) 1999 Harcourt Publishers Ltd.