Lecture 16 - Citric acid cycle 4 Flashcards
What is pyruvate carboxylase
Biotin requiring enzyme, Multifunction protein with two active sites
What is the multistep reaction catalysed by pyruvate carboxylase
Carboxylation of biotin and then transcarboxylation of pyruvate (slide 4)
How is Pyruvate carboxylase bonded to biotin
Covalently (biotin is Vitamin B7 - binds onto lysine residue of PC)
What are the sections of Pyruvate carboxylase
Biotin carboxyl carrier domain
Biotin carboxylation domain
Carboxytransferase domain (slide 6)
What is a homotetramer protein and why is pyruvate carboxylase an example of this
protein complex composed of four identical subunits each with an active site (slide 7)
What does the flexible nature of the lysine side chain allow
Allows for the transfer of molecule between active sites
Slide 10 - citric acid cycle
What is the glyoxylate cycle
A pathway in plants and bacteria to go from acetyl-CoA to sugars
Bacteria can grow on acetate
Plant seeds use fatty acids to make acetyl-CoA
In the glyoxylate cycle, what is the major difference to the citric acid cycle
Isocitrate is converted to succinate, producing glyocylate by isocitrate lyase
Glyocylate produced is then added to acetyl CoA and converted to malate by malate synthase
How do plants balance glyoxylate carboxylase and citric acid cycle
Separate organelle – glyoxysome where GC occurs
CAC occurs in mitochondria
How do bacteria balance the glyoxylate cycle and citric acid cycle
Only have isocitrate lyase and malate synthase when growing on acetate
Able to switch the genes on and off in response to substrate
Have both enzymes in the same compartment
Regulation is through isocitrate dehydrogenase (CAC cycle)
How does Isocitrate dehydrogenase controlled
IDH-Pi inactive form is hydrolysed by water and phosphatase to form IDH in its active form
Reverse is ATP-ADP forming IDH-Pi catalysed by a kinase
