Wechselzahl
the Wechselzahl determines, as well as the Michaeliskonstanten, the efficiency of an enzyme. This value, also “molecular activity “or” k cat “mentioned, characterizes the efficiency of an individual enzyme molecule:
- the Wechselzahl indicates, how many molecules substrate of the active center of the enzymefor each time unit (seconds) to be converted.
One keeps the Wechselzahl (k cat) divided by determination of the activity (V max) by the enzyme concentration (mol/l) in the test. It has the dimension k -1 (seconds of -1). Wechselzahlen move within the range of approximately 0.5 (Lysozym) and10.000.000, (Katalase).
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some examples
where, becomes in the right column the catalytic efficiency admits, i.e. the quotient from the Wechselzahl (k cat) and the Michaeliskonstante K m with aforementioned.
| Enzyme | substrate | Wechselzahl [mole substrate/second] | k cat /K m |
|---|---|---|---|
| Katalase | H 2 O 2 | 10.000.000 | 400.000.000 |
| Carboanhydrase | CO 2 | 1.000.000 | 83.000.000 |
| “ | HCO 3 | 400,000 | 15.000.000 |
| acetylcholinesterase | AcCh | 25,000 | 160.000.000 |
| urease | urea | 10,000 | 400,000 |
| Fumarase | Fumarat | 800 | 160.000.000 |
| “ | Malat | 900 | 36.000.000 |
| Kinasen | ATP | 1,000 | - |
| Trypsin, Chymotrypsin | of proteins | 100 -1.000 | - |
| Dehydrogenasen | NADH, H +, FADH 2 | 1,000 | - |
| DNA polymerases | DNA, NTP | 10 - 10,000 | - |
| - pole I | “ | 15 | - |
| - pole III | “ | 10,000 | - |
| Myosin ATPase | ATP | 100 | - |
| Aldolase | F1.6-BP | 100 | - |
| Lysozym | Murein | 0,5 | - |
See also: Enzyme kinetics.
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