Can you help me answer these short questions about the enzyme lactate dehydrogen

Question

Can you help me answer these short questions about the enzyme lactate dehydrogenase? Thank you in advance

1. How many isoforms of LDH are expressed in mammals? You will be purifying an LDH isoform from bovine muscle. This isoform is homologous to the LDH found in human muscle tissue. Would these bovine and human LDH homologs be considered orthologs, or paralogs 2. catalyzes the inter-conversion of Pyruvate and Lactate which is the more reduced form? 4. The catalytic mechanism for the inter-conversion of Pyruvate to Lactate requires the co- factor Nicotinamide Adenine Dinucleotide (NAD) What is the functional role of this co- factor? 5. In your initial lysis conditions, you will include the reagent (PMSF), which stands for Phenylmethulsulfonyl fluoride. What is the purpose of this reagent?

Explanation / Answer

1) 5 Isoforms of LDH are expressed in mammmals.

LDH-1 (4H)—in the heart and in RBC (red blood cells), as well as the brain.

2) Answer- Homolog. The term, homolog, is the relationship between genes separated by the event of speciation. Since Bovine and Humans are different species.
LDH-2 (3H1M)—in the reticuloendothelial system
LDH-3 (2H2M)—in the lungs
LDH-4 (1H3M)—in the kidneys, placenta, and pancreas
LDH-5 (4M)—in the liver and striated muscle

3) Pyruvate is the oxidized form while Lactate is the reduced form because of the difference of Ketone group in Pyruvate which is a more oxidized form vs Alcohol group in Lactate (less oxidized form). The conversion pf pyruvate to lactate is catalysed by lactate dehydrogenase which oxidises NADH, and hence reduces Pyruvate to Lactate.

4) Co Factors are inorganic molecules that are essential for Functioning and activity of an enzyme. NADH is a cofactor that acts as a reducing agent in the conversion of Pyruvate to Lactate. NADH act as electron carriers and transporters that ultimately transport the electrons to mitochindria in the Electron Transport Chain to generate energy in the form of ATP eventually.

5) PMSF is a serine protease inhibitor used in making cell lysates. PMSF specifically binds to Serine in the active site of the protein, this covalent binding helps in visualising the complex using X-ray crystallography. Therefore it can act as label to identify important active site in serine.

* Please consider leaving a thumbs up if the answer helps you. It would really go a long way to support my work. *

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.