Answer: The statements that correctly describe the structure of pyruvate dehydrogenase (PDH) complex are:
--> E2 contains three domains.
--> A regulatory kinase and phosphatase are part of the mammalian PDH complex.
--> Several copies each of E1 and E3 surround E2 .
Explanation:
Enzymes are proteins that speeds up a metabolic reaction by lowering the amount of energy needed to start the reaction. The type of enzyme in a cell will determine the metabolic processes that will occur in it.
Pyruvate dehydrogenase complex which is located at the mitochondria matrix, is a group of enzyme that catalyzes the breakdown of pyruvate, which is the end product of glycolysis, to form acetyl-CoA. The product formed from the reaction which is acetyl-CoA in turn enters the citric acid cycle where it is further oxidized for cellular respiration.
The structure of Pyruvate dehydrogenase complex consists of:
--> Three catalytic enzymes: These include;
• E1: This is the first enzyme of the PDH complex called pyruvate dehydrogenase. It catalyzes the removal of one carbon atom from pyruvate which leads to the production of hydrohyethyl.
• E2: This is the second enzyme of PDH complex called dihydrolipoamide S-acetyltransferase. It catalyzes the transfer of hydroxyethyl group to oxidized form of covalently bound lipoamide, and the resulting acetyl group is then transferred to free coenzyme A to form ACETYL-CoA and reduced dihydrolipoamide. Several copies each of E1 and E3 surround E2 and it consist of three DOMAINS. These domains include: N-terminal 9 kDa lipoyl domain, 4 kDa peripheral subunit-binding domain and C-terminal 28 kDa catalytic (acetyltransferase) domain.
• E3: This is the third and last enzyme of PDH complex called the flavoprotein dihydrolipoamide dehydrogenase. It re-oxidizes the lipoyl group of dihydrolipoamide-E2 to form lipoamide-E2 and NADH.
--> Two regulatory enzymes: The activities of E1 which is the rate limiting step of PDH complex regulated by phosphatases (activators) and kinases (inhibitors).
--> A binding protein: these aids in the binding of E2 to E3 enzyme in the core of PDH complex.