Catalyzes the condensation of pantoate with beta-alanine to form pantothenate. Essential for panthotenate biosynthesis. (R)-pantoate + ATP + beta-alanine = (R)-pantothenate + AMP + diphosphate + H(+) Enzyme kinetics do not match Michaelis-Menten kinetics, suggesting allosteric behavior. Inhibited by high pantoate levels. Optimum pH is 9.0. Cofactor biosynthesis; (R)-pantothenate biosynthesis; (R)-pantothenate from (R)-pantoate and beta-alanine: step 1/1. Homodimer. Expressed in roots, cotyledons, leaves, stems, cauline leaves, stigma, sepals and petals. Embryonic lethality due to arrest of embryogenesis at the preglobular stage when homozygous. Belongs to the pantothenate synthetase family.