Ubiquitin and ubiquitin-derived peptides as substrates for peptidylglycine α-amidating monooxygenase (original) (raw)

Ubiquitin (Ub) and the ubiquitin-like proteins (UBLs) mediate an array of cellular functions. These proteins contain a C-terminal glycine residue that is key to their function. Oxidative conversion of C-terminal glycine-extended prohormones to the corresponding a-amidated peptide is one step in the biosynthesis of bioactive peptide hormones. The enzyme catalyzing this reaction is peptidylglycine a-amidating monooxygenase (PAM). We report herein that Ub is a PAM substrate with a (V/K) amidation that is similar to other known peptide substrates. This work is significant because PAM and the UBLs co-localize to the hypothalamus and the adrenal medulla and are both overexpressed in glioblastomas.