This family of archaeal proteins includes pantothenate synthetase from Methanosarcina mazei and 4-phosphopantoate--beta-alanine ligase (phosphopantothenate synthetase) from Pyrococcus kodakaraensis. Pantothenate synthetase catalyses the condensation of pantoate with beta-alanine in an ATP-dependent and ADP-producing reaction [1]. 4-phosphopantoate--beta-alanine ligase catalyses the conversion of (R)-4-phosphopantoate and beta-alanine to 4'-phosphopantothenate in the CoA biosynthesis pathway. It cannot use (R)-pantoate as substrate and thus does not display pantothenate synthetase activity [2].

1: A novel isoform of pantothenate synthetase in the Archaea. Ronconi S, Jonczyk R, Genschel U; FEBS J. 2008;275:2754-2764. PMID:18422645

2: Pantoate kinase and phosphopantothenate synthetase, two novel enzymes necessary for CoA biosynthesis in the Archaea. Yokooji Y, Tomita H, Atomi H, Imanaka T; J Biol Chem. 2009;284:28137-28145. PMID:19666462