Characterization of glycerophosphoethanolamine ethanolaminephosphodiesterase from Streptomyces sanglieri

Streptomyces sanglieri extracellularly produces a glycerophosphoethanolamine ethanolaminephosphodiesterase (GPE-EP). The gene encoding the enzyme was found to consist of a 2124-bp ORF, which codes for an N-terminal 48 residue signal peptide required for secretion and a 660 amino acid mature protein with a calculated molecular mass of 72,918Da. The maximum activity for sn-glycero-3-phosphoethanolamine (GPE) was found at pH 8.4 and 65°C in the presence of 0.1% (w/v) Triton X-100. The enzyme was activated in the presence of 2mM EDTA; however, Zn²⁺ remarkably inhibited activity. During the hydrolysis of GPE at 65°C and pH 8.4, the apparent V_max, turnover number (k_cat) and K_m were determined to be 0.430mmolmin^-1mg-protein^-1, 522s^-1 and 0.785mM, respectively. The enzyme exhibited specificity toward GPE and hydrolyzed ethanolamine-type substrates such as 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine, lysophosphatidylethanolamine and ethanolamine lysoplasmalogen, but not 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine. Moreover, the enzyme showed no activity toward other phospholipids, such as glycerophospholipids and plasmalogens, and sn-glycero-3-phosphodiesters except for sn-glycero-3-phosphoglycerol, suggesting that GPE-EP is not a phospholipase C (PLC). However, the amino acid sequence of GPE-EP shows 86% identity to that of PLC from Streptomyces sp. SirexAA-E (UniProt accession no. G2NFN1). Recombinant GPE-EP was functionally expressed in Escherichia coli using pET-24a(+). GPE hydrolysis by GPE-EP may represent a new pathway for phosphatidylethanolamine metabolism.