Pregnancy Associated Plasma Protein-1 (PAPP-A) is a large zinc binding protein which acts as a metalloprotease and has been shown to cleave insulin-like growth factor binding protein-4. PAPP-A can act as a regulator of IGF bioactivity in several biological systems, including the human ovary and cardiovascular systems. Recent studies have shown that levels are elevated in patients with unstable angina or acute myocardial infarction. PAPP-A is also produced in high concentrations during pregnancy and is released into the maternal circulation. Low levels of PAPP-A have been linked with a number of fetal chromosomal abnormalities, as well as pre-eclampsia and stillbirth. Recombinant PAPP-A comprises a 191 amino acid fragment (81-271) corresponding to the PAPP-A ‘Jelly-Roll’ domain fragment and is expressed in E. coli with an amino-terminal hexahistidine tag.