1. The chymotrypsin catalytic triad contains one Histidine and one Serine residue. Explain, in some detail and in chemical terms, how an
a) a Histidine to Alanine mutation, and
b) a Serine to Cysteine mutation
in the chymotrypsin catalytic triad might affect catalytic activity of this enzyme.
2.
Kinetic properties of the two lactate dehydrogenase (LDH) isoforms are listed in the table below. The values are for the substrate pyruvate.
| Isoform | Kcat (s-1) | Km (mM) |
| H4 | 750 | 1 |
| M4 | 1360 | 0.1 |
Use the table to answer the following questions:
Assume that the total enzyme concentration is 1.0 nM and that the pyruvate concentration is 2 mM. What are the catalytic rates for the two isoforms? Don’t forget that both H4 and M4 are tetramers with 4 active sites!
Which isoform, H4 or M4, has a rate closest to its Vmax under the conditions in A? Justify your answer!
Estimate how long it would take (in minutes) for the isoform closer to Vmax in (B) to catalyze the conversion of 1 mmol pyruvate to lactate.
Show your calculations. No calculations - no points!
Kinetic properties of the two lactate dehydrogenase (LDH) isoforms are listed in the table below. The values are for the substrate pyruvate.
| Isoform | Kcat (s-1) | Km (mM) |
| H4 | 750 | 1 |
| M4 | 1360 | 0.1 |
Use the table to answer the following questions:
Assume that the total enzyme concentration is 1.0 nM and that the pyruvate concentration is 2 mM. What are the catalytic rates for the two isoforms? Don’t forget that both H4 and M4 are tetramers with 4 active sites!
Which isoform, H4 or M4, has a rate closest to its Vmax under the conditions in A? Justify your answer!
Estimate how long it would take (in minutes) for the isoform closer to Vmax in (B) to catalyze the conversion of 1 mmol pyruvate to lactate.
Show your calculations. No calculations - no points!Kinetic properties of the two lactate dehydrogenase (LDH) isoforms are listed in the table below. The values are for the substrate pyruvate.
| Isoform | Kcat (s-1) | Km (mM) |
| H4 | 750 | 1 |
| M4 | 1360 | 0.1 |
Use the table to answer the following questions:
Assume that the total enzyme concentration is 1.0 nM and that the pyruvate concentration is 2 mM. What are the catalytic rates for the two isoforms? Don’t forget that both H4 and M4 are tetramers with 4 active sites!
Which isoform, H4 or M4, has a rate closest to its Vmax under the conditions in A? Justify your answer!
Estimate how long it would take (in minutes) for the isoform closer to Vmax in (B) to catalyze the conversion of 1 mmol pyruvate to lactate.
Show your calculations. No calculations - no points!Kinetic properties of the two lactate dehydrogenase (LDH) isoforms are listed in the table below. The values are for the substrate pyruvate.
| Isoform | Kcat (s-1) | Km (mM) |
| H4 | 750 | 1 |
| M4 | 1360 | 0.1 |
Use the table to answer the following questions:
Assume that the total enzyme concentration is 1.0 nM and that the pyruvate concentration is 2 mM. What are the catalytic rates for the two isoforms? Don’t forget that both H4 and M4 are tetramers with 4 active sites!
Which isoform, H4 or M4, has a rate closest to its Vmax under the conditions in A? Justify your answer!
Estimate how long it would take (in minutes) for the isoform closer to Vmax in (B) to catalyze the conversion of 1 mmol pyruvate to lactate.
Show your calculations. No calculations - no points!
