What enzyme converts malate to oxaloacetate?

Malate dehydrogenase
Malate dehydrogenase (MDH) is an enzyme widely distributed among living organisms and is a key protein in the central oxidative pathway. It catalyzes the interconversion between malate and oxaloacetate using NAD+ or NADP+ as a cofactor.

How does oxaloacetate reduce malate?

In the cytosol, oxaloacetate is reduced to malate by electrons from NADH. Inside the mitochondrion, malate is oxidized by NAD+ back to oxaloacetate forming NADH. Oxaloacetate is transported back to the cytosol by the oxaloacetate/malate antiporter. In this way, NADH is transferred from cytosol into mitochondria.

What does malate do in the citric acid cycle?

Malate can be used to produce NADPH through its conversion to pyruvate by malic enzyme (ME), which is critical for providing the reducing power for building block synthesis. Oxaloacetate can be converted to aspartate, which plays a key role in nucleotide synthesis and amino acid synthesis.

What is malate converted to?

In the malate-pyruvate pathway, malate is exported from the mitochondria to the cytosol and converted directly to pyruvate by ME1.

Which enzyme is not present in TCA cycle?

Explanation: The only enzyme listed in the answer choices that does not catalyze a reaction within the citric acid cycle is pyruvate kinase. Pyruvate kinase is an important enzyme in the final step of glycolysis, as it catalyzes the conversion of phosphoenolpyruvate and ADP to pyruvate and ATP.

Is oxaloacetate oxidized or reduced?

Finally, malate is oxidized to form oxaloacetate. This reaction is catalyzed by malate dehydrogenase, and NAD+ is again the hydrogen acceptor. Note that the standard free energy for this reaction, unlike that for the other steps in the citric acid cycle, is significantly positive.

What does the Malate shuttle do?

The malate-aspartate (M-A) shuttle provides an important mechanism to regulate glycolysis and lactate metabolism in the heart by transferring reducing equivalents from cytosol into mitochondria.

Can malate leave the mitochondria?

6.4 The malate–aspartate shuttle The shuttle enables transfer of H+ from cytoplasmic NADH2 into the mitochondrial matrix and hence regenerates cytoplasmic NAD, and it also exports aspartate from the mitochondria.

What is malate used for?

It even acts as a natural antacid, a type of medication used to treat heartburn and relieve stomach upset ( 5 ). Magnesium malate can help increase your intake of magnesium and prevent deficiency. It may also help prevent headaches and act as a natural laxative and antacid.

How does malate become glucose?

Malate is oxidized to oxaloacetate using NAD+ in the cytosol, where the remaining steps of gluconeogenesis take place. This is also the rate-limiting step of gluconeogenesis. Glucose-6-phosphate is formed from fructose 6-phosphate by phosphoglucoisomerase (the reverse of step 2 in glycolysis).

What type of reaction is the conversion of fumarate to malate?

Fumarase (or fumarate hydratase) is an enzyme that catalyzes the reversible hydration/dehydration of fumarate to malate. Fumarase comes in two forms: mitochondrial and cytosolic.

How many ATP are formed in TCA cycle?

2 ATPs
2 ATPs are produced in the TCA cycle per glucose molecule (2 acetyl CoA).

What is the coupling reaction of malate to oxaloacetate?

Coupling reactions. The oxidation of malate by NAD + to form oxaloacetate is a highly endergonic reaction under standard conditions [ΔG°′ + 7 kcal mol -1 (+ 29 kJ mol -1)]. The reaction proceeds readily under physiological conditions.

How does the malate-aspartate shuttle system work?

Malate-Aspartate Shuttle Mammalian tissues can use a shuttle system involving malate and aspartate to transport electrons across the mitochondrial inner membrane. Oxaloacetate in the cytoplasm is converted to malate by malate dehydrogenase, oxidizing NADH to NAD.

What happens when malate is oxidized to OAA?

Malate is oxidized to OAA with production of NADH; this returns the cycle to the beginning, with OAA available to condense with another molecule of acetyl-CoA. Exchange between the mitochondrial matrix and the cytoplasm is highly selective and requires specific transporters.

How is malate extracted from the mitochondria?

Malate and the electrons it carries are transported into the mitochondria across the inner mitochondrial membrane, in exchange for alpha-ketoglutarate, which is transported out of the mitochondria. Once inside, the energy in malate is extracted again by reducing NAD+ to make NADH, regenerating oxaloacetate.