Bacterial phosphatidylethanolamine biosynthesis through phosphatidylserine

A reusable two-reaction bacterial module for phosphatidylethanolamine biosynthesis from CDP-diacylglycerol. PssA transfers a phosphatidyl group to L-serine to form phosphatidylserine, and pyruvoyl-dependent Psd decarboxylates phosphatidylserine to phosphatidylethanolamine.

The module begins with CDP-diacylglycerol and L-serine and ends with phosphatidylethanolamine. CDP-diacylglycerol synthesis, phosphatidylglycerol and cardiolipin branches, lipid acyl-chain remodeling, and alternative phosphatidylethanolamine routes such as the Kennedy pathway are outside the boundary. Psd autocatalytic maturation is required for activity but is a property of the terminal enzyme rather than a separate pathway reaction. Bacterial phosphatidylserine synthases occur in mechanistically distinct type-I and type-II architectures. These type names follow the PssA nomenclature of PMID:39693441; UniProt's CDP-alcohol phosphatidyltransferase class-I/class-II family labels describe a different classification axis and appear inverted relative to the PssA type names. KT2440 encodes candidates from both types; their relative physiological contributions have not been resolved.