Description
PGP9.5 is a soluble cytoplasmic protein with a molecular weight of approximately 25,000 kD. It is present in neurons and in cells of the diffuse neuroendocrine system. PGP9.5 functions as a tissue-specific ubiquitin carboxyl terminal hydrolase isoenzyme. This enzyme is also known as UCH-L1. Because of its abundance in nerves, it has been widely used as a marker for peripheral nerve fibers.
It was also discovered as a gene mutated in some rare famial forms of Parkinson's disease. Interestingly a common allelic variant of UCHL1, the S18Y polymorphism is actually protective against Parkinson's disease. It is also a marker for cells of the diffuse neuroendocrine system and their tumors