Question

You are overseeing a person who has developed seizures following a prolonged fast. Which of the following could explain this observation?

	A.	Mutation in acetyl-CoA carboxylase (ACC) that precludes binding of citrate to the enzyme’s regulatory domain
	B.	Mutation in pancreatic lipase that inhibits its activity
	C.	Mutation in the Glut45 transporter at the blood brain barrier that inhibits its activity
	D.	Mutation in HMG-CoA lyase that inhibits its activity
	E.	Mutation in the low density lipoprotein (LDL) receptor that increases its degradation in lysosomes

Answer 1

The correct option is D.(Mutation in HMG- CoA lyase that inhibits it's activity.)

3 hydroxy 3 methyl glutaryl CoA lyase (HMG-CoA lyase) is one of the key enzyme involved in ketogenesis. Ketogenesis is very crucial for sugar and energy production during fasting, When a person fasts for prolonged time period then energy or sugar to cells are supplied by breaking down fat molecules and ketogenesis, If ketogenesis will be affected then there will be poor supply of glucose and energy to brain cells and that can cause seizures. Mutation in HMG CoA lyase is one of the key reason for hypoketotic hypoglycemia as it is also involved in breakdown of a key ketogenic amino acid leucine.

The enzyme helps in conversion of HMG Co A to acetoacetate in mitochondria. This enzyme is most abundantly found in liver cells.

Option A is incorrect-Acetyl CoA carboxylase is related to fatty acid biosynthesis by carboxylating acetyl CoA and converting it into Malonyl CoA. Since fatty acid biosynthesis can in no way contribute for maintaining energy level in a starving person. Hence, this option is incorrect.

Option B is also incorrect. Pancreatic lipase is key lipid digesting enzyme. It performs hydrolysis of ester bonds found in triglycerides. Here, since the person is not eating anything. There is no question of any issue happening because of dysfunctional digestive enzyme. Hence, this option is incorrect.

Option C is incorrect. GLUT transporters/ glucose transporters are important for transport of glucose inside the cell. If there will be mutation in glucose transporter at the blood brain barrier then the person will not be able to live normally even in a well fed state. Since, here the situation of disease arose only after prolonged fasting. Therefore, situation can not be related to glucose transporter. Hence, this option is incorrect.

Option E is also incorrect. Mutation in Low density lipid receptor will only affect absorption of cholesterol along with low density lipid, LDL receptor recognizes the apolipoprotein ApoB100 and helps in receptor mediated endocytosis. Mutation in LDL receptor causes Hypercholesterolemia and atherosclerosis, due to high continuous high level of cholesterol and lipid in the blood.