(1) An enzyme catalyzes a reaction in which substrate A is cleaved into two products, P and Q. In the catalytic mechanism, the enzyme converts A to an covalently-bound reaction intermediate X and product P, P then desorbs from the enzyme, and in a second chemical step, the enzyme converts the intermediate X in the EX complex to the final product Q (in EQ), which then desorbs from the enzyme E. k3 k7 k1 k9 ks E A EA E Q EXP EX EQ k2 k4 kg You discover two inhibitors of this enzyme, I and J. I is a competitive inhibitor of the substrate A, and has nearly double the molecular weight of J. On the other hand, J is a mixed inhibitor of enzyme E, and its inhibitory effect on Km/ Vmax (the slope effect from the double reciprocal plot) is greater than that of 1/Vmax (the intercept effect in a double reciprocal plot). That is Kis < Kji At low pH, the conversion of EX to EQ is greatly slowed, kcat is decreased, and the intercept effect of inhibitor J is elevated, that is, the value of Ki is diminished. When a high, fixed concentration of product P is added to the enzymatic reaction, the inhibition due to inhibitor I is unchanged, but inhibitor J becomes a competitive inhibitor vs. A. (1) To which enzyme forms do I and J bind? Explain how you got there. I cannot bind when A is at a concentration of infinity (no intercept effect). I is competitive vs. A and therefore binds to E. I may structurally resemble substrate A Jis a mixed inhibitor; it exerts both a slope effect and an intercept effect, but the slope effect is more significant than the intercept effect: Kis< Kji. J probably binds to E twice: to E to form EJ, which gives rise to the slope effect, and the intercept effects comes from binding to EA, or a downstream complex such as EXP, EX, or EQ. J has structural features similar to I, which is why it can bind to E, but is smaller than Iand can fit into another pocket during catalysis At low pH, chemical steps are slowed, especially the conversion of EX > EQ, and inhibition arises from the intercept effect becomes tighter. This must mean that the [EX] at low pH increases, it piles up because its breakdown is slowed, and it allows more binding of J to EX to make EXJ. Addition of P to the reaction prevents the effect of J on the intercept effect of the mixed inhibition, because the EX complex is converted to EXP, and J can no longer bind to EX, but it may still bind to E I binds to E. J binds to E and also to EX, but better binding to E I and J both resemble substrate A, but since J is smaller than I, it fits into the substrate-binding site of E on the "P" side of the substrate binding site. (2) What is the likely rate-limiting step for this enzyme? Explain. Since J has an effect on the intercept effect of inhibition, and it was shown that it must bind to the EX complex, then the conversion of EX => EQ is the slowest step in the reaction. (3) Since the enzyme E cleaves substrate A into two products, P and Q, which inhibitor has the most structural resemblance to A?. Of the three ligands A, P, and Q, which does/do J structurally resemble? Explain is more like A than J. I is also like both P and Q, but J is like P.
Enzyme kinetics
In biochemistry, enzymes are proteins that act as biological catalysts. Catalysis is the addition of a catalyst to a chemical reaction to speed up the pace of the reaction. Catalysis can be categorized as either homogeneous or heterogeneous, depending on whether the catalysts are distributed in the same phase as that of the reactants. Enzymes are an essential part of the cell because, without them, many organic processes would slow down and thus will affect the processes that are important for cell survival and sustenance.
Regulation of Enzymes
A substance that acts as a catalyst to regulate the reaction rate in the living organism's metabolic pathways without itself getting altered is an enzyme. Most of the biological reactions and metabolic pathways in the living systems are carried out by enzymes. They are specific for their works and work in particular conditions. It maintains the best possible rate of reaction in the most stable state. The enzymes have distinct properties as they can proceed with the reaction in any direction, their particular binding sites, pH specificity, temperature specificity required in very few amounts.
An enzyme catalyzes a reaction in which substrate A is cleaved into two products, P and Q. In the catalytic mechanism, the enzyme converts A to an covalently-bound reaction intermediate X and product P, P then desorbs from the enzyme, and in a second chemical step, the enzyme converts the intermediate X in the EX complex to the final product Q (in EQ), which then desorbs from the enzyme E. You discover two inhibitors of this enzyme, I and J. I is a competitive inhibitor of the substrate A, and has nearly double the molecular weight of J. On the other hand, J is a mixed inhibitor of enzyme E, and its inhibitory effect on Km / Vmax (the slope effect from the double reciprocal plot) is greater than that of 1 / Vmax (the intercept effect in a double reciprocal plot). That is Kis < Kii .
At low pH, the conversion of EX to EQ is greatly slowed, kcat is decreased, and the intercept effect of inhibitor J is elevated, that is, the value of Kii is diminished.
When a high, fixed concentration of product P is added to the enzymatic reaction, the inhibition due to inhibitor I is unchanged, but inhibitor J becomes a competitive inhibitor vs. A.
(1) To which enzyme forms do I and J bind? Explain how you got there.
I cannot bind when A is at a concentration of infinity (no intercept effect). I is competitive vs. A and therefore binds to E. I may structurally resemble substrate A. J is a mixed inhibitor; it exerts both a slope effect and an intercept effect, but the slope effect is more significant than the intercept effect: Kis < Kii. J probably binds to E twice: to E to form EJ, which gives rise to the slope effect, and the intercept effects comes from binding to EA, or a downstream complex such as EXP, EX, or EQ. J has structural features similar to I, which is why it can bind to E, but is smaller than I and can fit into another pocket during catalysis.
At low pH, chemical steps are slowed, especially the conversion of EX => EQ, and inhibition arises from the intercept effect becomes tighter. This must mean that the [EX] at low pH increases, it piles up because its breakdown is slowed, and it allows more binding of J to EX to make EXJ.
Addition of P to the reaction prevents the effect of J on the intercept effect of the mixed inhibition, because the EX complex is converted to EXP, and J can no longer bind to EX, but it may still bind to E.
I binds to E. J binds to E and also to EX, but better binding to E.
I and J both resemble substrate A, but since J is smaller than I, it fits into the substrate-binding site of E on the “P” side of the substrate binding site.
(2) What is the likely rate-limiting step for this enzyme? Explain. Since J has an effect on the intercept effect of inhibition, and it was shown that it must bind to the EX complex, then the conversion of EX => EQ is the slowest step in the reaction.
(3) Since the enzyme E cleaves substrate A into two products, P and Q, which inhibitor has the most structural resemblance to A?. Of the three ligands A, P, and Q, which does/do J structurally resemble? Explain. I is more like A than J. I is also like both P and Q, but J is like P.
![At low pH, chemical steps are slowed, especially the conversion of EX > EQ, and inhibition arises
from the intercept effect becomes tighter. This must mean that the [EX] at low pH increases, it piles
up because its breakdown is slowed, and it allows more binding of J to EX to make EXJ.
Addition of P to the reaction prevents the effect of J on the intercept effect of the mixed inhibition,
because the EX complex is converted to EXP, and J can no longer bind to EX, but it may still bind to E
I binds to E. J binds to E and also to EX, but better binding to E
I and J both resemble substrate A, but since J is smaller than I, it fits into the substrate-binding site
of E on the "P" side of the substrate binding site.
(2) What is the likely rate-limiting step for this enzyme? Explain. Since J has an effect on the
intercept effect of inhibition, and it was shown that it must bind to the EX complex, then the
conversion of EX => EQ is the slowest step in the reaction.
(3) Since the enzyme E cleaves substrate A into two products, P and Q, which inhibitor has the
most structural resemblance to A?. Of the three ligands A, P, and Q, which does/do J
structurally resemble? Explain
is more like A than J. I is also like both P and Q, but J is like P.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F224b4099-5fc1-4076-a1db-953078e76a72%2F21056591-b46e-4346-9f5e-639298d002a0%2Fz3tiepp.png&w=3840&q=75)
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