Deficient in Lactase (Lactose intorlerant)
Galactose Is Toxic If Transferase Missing
The Glycolytic Pathway Is Tightly Controlled
3. Pyruvate kinase
Methods of regulation
1. allosteric regulation
2. covalent modification
the key point for regulation of glycolysis
allosteric activator：AMP; F-2,6-BP (in the liver)
allosteric inhibitor：ATP; citrate
In high concentrations, fructose 6-phosphate (F-6P) activates the enzyme phosphofructokinase (PFK) through an intermediary, fructose 2,6-bisphosphate (F-2,6-BP).
F-6P to PFK if too many Glucose(by insulin)
Hexokinase is suppressed by its product G-6-P.
Glucokinase in liver, is not inhibited by G-6-P.
Glucokinase phosphorylates glucose only when glucose is abundant
The role of glucokinase is to provide G-6-P for the synthesis of glycogen and for the formation of fatty acids.
Gives the brain and muscles first call on glucose when its supply is limited, and it ensures that glucose will not be wasted when it is abundant.
Glycolysis and Gluconeogenesis back and forth
from Noncarbohydrate Precursors to Glucose
The gluconeogenic (糖異生) pathway converts pyruvate into glucose.
Gluconeogenesis is not a reversal of glycolysis
Noncarbohydrate precursors are first converted into pyruvate, oxaloacetate, dihydroxyacetone phosphate.
Noncarbohydrate Precursors: lactate, amino acids, and glycerol.
pathway of Gluconeogenesis