PAPP-A CLIA

Maternal serum concentrations of pregnancy-associated plasma protein A (PAPP-A, EC 3.4.24.79, papalysin-1) are used to predict occurrence of Down syndrome. During pregnancy, PAPP-A is produced in high concentrations by the trophoblast and released into maternal circulation. In pregnancy, PAPP-A primarily circulates as 500-kDa heterotetrameric 2:2 complex with the proform of eosinophil major basic protein (proMBP), which inhibits the proteolytic activity of PAPP-A. Dimeric PAPP-A is the only active form and proteolyses IGFBP-4 and IGFBP-5. Significant amounts of active PAPP-A is reported at gestational ages between seven and thirteen weeks.

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