Wk 4 - Pentose Phosphate Deficiencies

Question 1

Essential fructosuria

Answer 1

• Benign
• Fructokinase is deficient
• Can’t convert fructose to glucose
• CAN use hexokinase — makes fructose 6-phosphate… glycolytic intermediate
• Extra fructose excreted in the urine

Question 2

Hereditary fructose intolerance

Answer 2

• NOT BENIGN
• Aldolase B deficiency (in liver)
• So…fructose can go through GLUT5 and be phosphorylated by fructokinase… but everything is stuck as fructokinase because aldolase B can turn it into a glycolytic intermediate
• Becomes metabolic phosphate sink
• Causes: lactic acidosis, ATP deficiency, hypoglycemia, liver failure

Question 3

Galactose 1-phosphate uridyl transferase deficiency

Answer 3

“Classical galactosemia”

• Super serious
• Locks up phosphate as galactose 1-phosphate
• No place for galactose 1-phosphate to go without the uridyl transferase
• Causes liver failure and jaundice

Question 4

Galactokinase deficiency

Answer 4

Hypergalactosemia

• Too much galactose because not being converted to galactose 1-P and going on to glycolysis/glycogenesis
• Galactose builds up in the eye and goes through the polyl pathway
• —- Leads to cataracts

Question 5

UDP-galactose 4 epimerase deficiency

Answer 5

• Lockup of phosphate groups because galactose 1-P can’t turn into UDP glucose

Serious form affects all tissues - similar to galactosemia

Don’t eat lactose

Question 6

Glucose 6-phosphate dehydrogenase deficiency

Answer 6

• G6P dehydrogenase = first enzyme in pentose phosphate pathway
• Much slower than normal
• Can’t do the PPP reactions so… less NADPH, less glutathione (so causes ROS), less glycolytic intermediates
• Can cause hydroxyl radicals