Suppose a new patient, patient HLU, presents with fatigue and failure to thrive within a few days. Upon further investigation, it is discovered that HLU has hypoglycemia between feedings and lactic acidosis right after feeding. In addition, isoelectric focusing of the protein transferrin from his bloodstream,
Suppose a new patient, patient HLU, presents with fatigue and failure to thrive within a few days. Upon further investigation, it is discovered that HLU has hypoglycemia between feedings and lactic acidosis right after feeding. In addition, isoelectric focusing of the protein transferrin from his bloodstream, transferrin being a heavily glycosylated protein, reveals that HLU has erroneous N-linked glycosylation of transferrin. Biosynthesis of N-linked glycosylated glycoproteins require UDP-glucose and UDP-galactose for construction of the oligosaccharide that gets added to the protein in the endoplasmic reticulum. Muscle biopsy later in life reveals that he has a glycogen storage disease – there are excess amounts of normally structured glycogen in muscle cells.
Early in life, he was subjected to the Beutler test and misdiagnosed with galactosemia because NADPH levels did not increase as readily as wild type patient upon administration of galactose. Which enzyme is deficient in HLU?
Why does this deficiency cause hypoglycemia between feeding, lactic acidosis after feedings, and excess, normal glycogen?
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