(R)-pantolactone + A <=> 2-dehydropantolactone + AH2
(r)-pantolactone + a <=> 2-dehydropantolactone + ah2
(R)-pantolactone + A <=> 2-dehydropantolactone + AH2
(r)-pantolactone + a <=> 2-dehydropantolactone + ah2