Rate Determining Enzymes

Question 1

Glycolysis

Answer 1

Substrate Fructose -1 phosphate
Phosphofructokinase
Regulators
+ AMP, fructose 2,6 bisphophate
- ATP, citrate
End product pyruvate

Question 2

Gluconeogenesis

Answer 2

Pyruvate —-> glucose

Rate limiting enz:- fructose 1,6 bisphosphatase

Stimulated by citrate and glucagon
Inhibited:- AMP, fructose 2,6 bisphosphate

Fructose 1,6 bisphospahte —> fructose 6 phosphate

Co-factors needed in pathway:- biotin + acetyl CoA for pyruvate kinase

Question 3

Glycogenesis

Answer 3

Glucose ——> glycogen

Rate limiting enz:- glycogen synthase

Stimulated:= insulin, glucose 6 phosphate, cortisol

Inhibited:- epinephrine, glucagon

Question 4

Glycogenolysis

Answer 4

Glycogen ——> glucose

Rate limiting enz:- glycogen phosphorylase

Stimulated:- glucagon, epinephrine, cAMP

Inhibited:- insulin, glucose 6 phosphate and ATP

Occurs in cytoplasm

Question 5

Von Gierke

Answer 5

Glucose 6 phosphate —-> glucose defect

Deficient enz:- glucose 6 phosphatase

Presentation:- hepatomegaly, hyperlipidaemia, hyperuricaemia, hypoglyaemia, hyperuricaemia, high bld lactate
High glucose 6 phosphate

Question 6

Cori’s disease

Answer 6

Glucose 1 phosphate —-> glucose 6 phosphate defect

Deficiency:- amylo 1,6 glucosidase - debranching enzyme

Presentation:- milder von gierke abnormal branching glycogen, hyoglycaemia, hepatomegaly, mild myopathy 2o glycogen deposition

Question 7

Mcardle disease

Answer 7

Enz deficiency:- glycogen phophorylase (muscle)

Presentation:- In muscle. In liver
muscle cramps with exercise. Hepatomegaly
Hypoglycaemia with exercise. Fasting hypoglycaemia
Myoglobulinuria
Labs:- high CK

Question 8

Andersen’ s disease

Answer 8

Enz deficiency:- lack of branching enzyme
Glycogen long single chain

Presentation:- infant cirrhosis, hypotonia, cardiomyopathy, fatal