ANSC 221

Kinase

Adds phosphate

Isomerase

Creates isomers

Mutase

Specific type of Isomerase that moves entire functional groups

Dehydrogenase

Moves hydrogen atoms from molecule

Phosphatase

Removes phosphate group

Phosphorylase

Cleaves bonds from inorganic phosphate

Synthase

Synthesize new molecules without using energy

Synthetase

Synthesize new molecules using energy

Transaminase

Transfers an amino group onto a molecule that does not already have one

Transferase

Move entire functional groups from one compound to another

Reductase

Catalyzes reduction of the substrate, often consuming a reduced, reducing equivalent

Lipase

Breaks down lipids

What enzyme links the TCA cycle and lipogenesis?

Citrate Synthase

Function: Condenses acetyl-CoA + oxaloacetate → citrate, which can be exported to the cytosol for fatty acid synthesis.

What enzyme produces ATP from the proton gradient in oxidative phosphorylation?

ATP Synthase

Function: Uses the proton motive force to convert ADP + Pi → ATP.

What protein dissipates the proton gradient without making ATP?

Uncoupling Protein (UCP)

Function: Allows protons to flow back into the matrix, releasing energy as heat (non-shivering thermogenesis).

What is the purpose of these shuttles?

To transfer cytosolic NADH electrons into mitochondria for oxidative phosphorylation.

Glycerol-Phosphate Shuttle:

Transfers electrons to FAD → FADH₂ (less ATP yield).

Malate-Aspartate Shuttle:

Transfers electrons to NAD⁺ → NADH (higher ATP yield).

Which enzyme connects the TCA cycle and urea cycle?

Aspartate Aminotransferase (AST / Transaminase)

Function: Converts oxaloacetate ↔ aspartate, linking carbon flow (TCA) with nitrogen flow (urea cycle).

What enzyme is shared between β-oxidation and ketogenesis?

Thiolase (Acetyl-CoA Acetyltransferase)

Function:

• In β-oxidation, cleaves fatty acyl-CoA → acetyl-CoA.
  
  

• In ketogenesis, condenses two acetyl-CoA → acetoacetyl-CoA.

What enzyme determines whether pyruvate enters the TCA cycle or becomes lactate?

• Pyruvate Dehydrogenase (PDH): Converts pyruvate → acetyl-CoA (aerobic).
  
  

• Lactate Dehydrogenase (LDH): Converts pyruvate ↔ lactate, regenerating NAD⁺ for glycolysis (anaerobic).

What is the rate-limiting enzyme in fatty acid synthesis?

Acetyl-CoA Carboxylase (ACC)

Function: Converts acetyl-CoA → malonyl-CoA (committed step of lipogenesis).

Regulation:

• Activated by citrate and insulin.
  
  

• Inhibited by palmitoyl-CoA and glucagon.