<prompt> Absence of which of the following enzyme in humans is responsible for the inability to synthesize ascorbic acid?L-Glucuronic acid oxidaseL-Gulonic acid reductaseL-Gulonolactone oxidaseL-Gulonolactone reductase  <response>: Uronic acid pathway is an alternate pathway for oxidation of glucose without ATP formation. Fig: Uronic acid pathway An intermediate L-gluconate of this pathway can be used for the synthesis of ascorbic acid in plants by enzyme L-gulonolactone oxidase. However, In human beings and other primates, as well as guinea pigs, bats, and some birds and fishes, ascorbic acid cannot be synthesized because of the absence of L-Gulonolactone oxidase. 