Catalyzes the NAD(P)(+)-dependent conversion of L-arabinose to L-arabino-gamma-lactone. Is involved in a degradation pathway of L-arabinose that allows A.brasilense to grow on L-arabinose as a sole carbon source. Prefers NADP(+) to NAD(+) as electron acceptor. Displays high catalytic efficiency for both L-arabinose and D-galactose in vitro. However, the enzyme appears to be involved in the metabolism of L-arabinose but not D-galactose in vivo. To a lesser extent, is also active on D-talose and D-xylose as substrates in vitro, but not with D-arabinose, D-glucose, D-ribose, L-xylose, L-mannose, L-lyxose, and D-fructose. alpha-L-arabinopyanose + NAD(+) = H(+) + L-arabinono-1,4-lactone + NADH alpha-L-arabinopyanose + NADP(+) = H(+) + L-arabinono-1,4-lactone + NADPH D-galactose + NAD(+) = D-galactono-1,4-lactone + H(+) + NADH D-galactose + NADP(+) = D-galactono-1,5-lactone + H(+) + NADPH Carbohydrate degradation; L-arabinose degradation via L-arabinono-1,4-lactone pathway. Monomer. Induced by L-arabinose but not by D-galactose, D-xylose and D-glucose. Cells lacking this gene do not grow on L-arabinose as a sole carbon source but grow on D-galactose, D-xylose or D-glucose at the same growth rate as the wild-type strain. Belongs to the Gfo/Idh/MocA family.