PLA2G-VII which is also known as Lp-PLA2, is a plasma enzyme bound to lipoproteins: 80% bound to LDL, 15%-20% to HDL, and the remainder to VLDL. It is produced in major by mature macrophages and activated platelets. In contrast to other classical sPLA2s, PLA2G-VII has poor specificity toward Sn-2 long chain fatty acids, unless heavily oxidized, and undergoes the catalysis of its substrates in the aqueous phase rather than at the interfacial surface of lipids. Thus, it has high specificity for water-soluble phospholipids in plasma including oxidatively-modified phospholipids and platelet-activating factor (PAF). Because of the latter activity, it is also known as PAF acetylhydrolase (PAF-AH). Lack of human PLA2G-VII is related to a higher risk for stroke and heart disease.The activity of recombinant rat PLA2G-VII was measured by its ability to cleave a colorimetric peptide substrate 1-O-hexadecyl-2-deoxy-2-thio-S-acetyl-sn-glyceryl-3-phosphorylcholine (2-Thio-PAF). The reaction was performed in 50 mM MES, 150 mM NaCl, 0.1 mg/mL BSA, pH 6.5 (Assay Buffer), initiated by addition 50 μL of various concentrations of PLA2G-VII (diluted by Assay Buffer) to 50 µL of 0.2 mM Substrate and 0.2 mM DTNB mixture. The final well serves as a negative control with no PLA2G-VII, replaced with 50 μL assay buffer. Then read absorbance at 405 nm in kinetic mode for 5 minutes. The specific activity of recombinant rat PLA2G-VII is 112.37 pmol/min/µg.