Proteinase inhibitor 6 (PI-6) is a 42 kDa cytoplasmic protein belonging to the serine proteinase inhibitor (serpin) super family and the ovalbumin-serpin super family. Sequence similarity sμggests that PI-6 most resembles the ovalbumin serpins . Highest levels of PI-6 are found in skeletal muscle. PI-6 is also found in placenta, cardiac muscle, lung, liver, kidney and pancreas.