Overview Amino acid absorption in intestine proteins degraded by trypsin and pepsin enteropeptidase cleaves trypsinogen (inactive) to trypsin (active) absorbed as amino acids across the gut lumen with a specific transporter for difference classes of amino acids transporter for basic amino acids; transporter for large neutral amino acids deficiencies lack of absorption with pancreatitis due to ↓ in degradative enzyme production Hartnup disease defect in large neutral amino acid transporter result is a tryptophan deficiency presents similar to pellagra