This group contains class II terpene cyclases, protein prenyltransferases beta subunit, two broadly specific proteinase inhibitors alpha2-macroglobulin (alpha (2)-M) and pregnancy zone protein (PZP) and, the C3 C4 and C5 components of vertebrate complement. Class II terpene cyclases include squalene cyclase (SQCY) and 2,3-oxidosqualene cyclase (OSQCY), these integral membrane proteins catalyze a cationic cyclization cascade converting linear triterpenes to fused ring compounds. The protein prenyltransferases include protein farnesyltransferase (FTase) and geranylgeranyltransferase types I and II (GGTase-I and GGTase-II) which catalyze the carboxyl-terminal lipidation of Ras, Rab, and several other cellular signal transduction proteins, facilitating membrane associations and specific protein-protein interactions. Alpha (2)-M is a major carrier protein in serum and involved in the immobilization and entrapment of proteases. PZP is a pregnancy associated protein. Alpha (2)-M and PZP are known to bind to and, may modulate, the activity of placental protein-14 in T-cell growth and cytokine production thereby protecting the allogeneic fetus from attack by the maternal immune system.
Cyclases involved in the biosynthesis of lantibiotics, and similar proteins. LanC is the cyclase enzyme of the lanthionine synthetase. Lanthionine is a lantibiotic, a unique class of peptide antibiotics. They are ribosomally synthesized as a precursor peptide and then post-translationally modified to contain thioether cross-links called lanthionines (Lans) or methyllanthionines (MeLans), in addition to 2,3-didehydroalanine (Dha) and (Z)-2,3-didehydrobutyrine (Dhb). These unusual amino acids are introduced by the dehydration of serine and threonine residues, followed by thioether formation via addition of cysteine thiols, catalysed by LanB and LanC or LanM. LanC, the cyclase component, is a zinc metalloprotein, whose bound metal has been proposed to activate the thiol substrate for nucleophilic addition. A related domain is also present in LanM and other pro- and eukaryotic proteins with poorly characterized functions.
This group contains class II terpene cyclases, protein prenyltransferases beta subunit, two broadly specific proteinase inhibitors alpha2-macroglobulin (alpha (2)-M) and pregnancy zone protein (PZP) and, the C3 C4 and C5 components of vertebrate complement. Class II terpene cyclases include squalene cyclase (SQCY) and 2,3-oxidosqualene cyclase (OSQCY), these integral membrane proteins catalyze a cationic cyclization cascade converting linear triterpenes to fused ring compounds. The protein prenyltransferases include protein farnesyltransferase (FTase) and geranylgeranyltransferase types I and II (GGTase-I and GGTase-II) which catalyze the carboxyl-terminal lipidation of Ras, Rab, and several other cellular signal transduction proteins, facilitating membrane associations and specific protein-protein interactions. Alpha (2)-M is a major carrier protein in serum and involved in the immobilization and entrapment of proteases. PZP is a pregnancy associated protein. Alpha (2)-M and PZP are known to bind to and, may modulate, the activity of placental protein-14 in T-cell growth and cytokine production thereby protecting the allogeneic fetus from attack by the maternal immune system.
