Q. A 24-year-old man presents to the emergency department with severe abdominal pain. He describes the pain as continuous and radiating to the back. His medical history is notable for repeated episodes of pruritic skin eruptions. Physical examination reveals a mildly distended abdomen with tenderness to palpation in the epigastric region. A CT scan of the abdomen confirms the suspicion of acute pancreatitis. His fasting lipid panel shows markedly elevated triglycerides and a creamy layer is observed on the top of his blood sample in a test tube. Based on the patient's presentation and laboratory findings, which of the following deficiencies is most likely contributing to his condition?