Pregnancy-associated plasma protein-A

Introduction

Pregnancy-associated plasma protein-A (PAPP-A) largest of the pregnancy associated proteins produced by both the embryo and the placenta (syncytiocytotrophoblasts) during pregnancy (Placenta Notes). This protein is thought to have several different functions, including preventing recognition of the fetus by the maternal immune system, matrix mineralization and angiogenesis. Levels of PAPP-A rise from first detection in the first trimester until term.

Detection of this protein is also suggested as a first and second trimester diagnostic test for aneuploidies, including Trisomy 21 or Down Syndrome.

Maternal serum concentrations are related to subsequent fetal growth and this relationship has suggested that it can be used as a diagnostic test for adverse pregnancy outcomes (intrauterine growth restriction, premature birth, preeclampsia, and stillbirth).

Alternative names: pappalysin 1, PAPP-A, PAPPA1, SP4, high molecular weight alpha-2 mobile pregnancy-specific protein, IGFBP4 protease (IGFBP-4ase), ASBABP2, DIPLA1, PAPA

| Original PAPP-A page

PAPP-A Levels

Levels of PAPP-A rise from initial detection at about 32 days after ovulation, then increasing rapidly (levels doubling every 3 days), finally continuing to rise more slowly until term.

Electroimmunoassays allow the detection as early as the fifth week of pregnancy, of circulating levels down to 10 microgram/L.

Adult male serum PAPP-A circulating level is 8.03±2.75 mIU/L (mean±SD).

Protein

• large zinc glycoprotein
• secreted metalloproteinase (EC=3.4.24.79) which cleaves insulin-like growth factor binding proteins (IGFBPs).
  • specifically cleaves IGFBP-4 and IGFBP-5, releasing bound IGF
• placental origin
• also in: ovarian follicles, follicular fluid, luteal cells
  • uterine tubes of nonpregnant women
  • seminal vesicles and seminal fluid of males

Links: OMIM | GeneCards | UniProtKB/Swiss-Prot