a 1,2-diacyl-sn-glycero-3-phospho-L-serine + H(+) = a 1,2-diacyl-sn-glycero-3-phosphoethanolamine + CO2 Binds 1 pyruvoyl group covalently per subunit. Phospholipid metabolism; phosphatidylethanolamine biosynthesis; phosphatidylethanolamine from CDP-diacylglycerol: step 2/2. Belongs to the phosphatidylserine decarboxylase family. Type 1 subfamily.