Table II.
Substrate specificity of A. cepa root alliinase isoforms I and II, with MCSO, ECSO, PCSO, AllylCSO, PrenCSO, cystine, Cys, methyl-l-Cys, and cystathionine
| Substrate | Isoform
I
|
Vmax/Km | Isoform
II
|
Vmax/Km | ||
|---|---|---|---|---|---|---|
| Km | Vmax | Km | Vmax | |||
| mm | nkat/mg | mm | nkat/mg | |||
| MCSO | 47.0 ± 12.7 | 5,412 ± 564 | 115 | 96.6 ± 16.6 | 5,251 ± 569 | 54 |
| ECSO | 45.7 ± 15.7 | 25,013 ± 3,693 | 547 | 68.4 ± 9.5 | 28,568 ± 2,730 | 418 |
| PCSO | 22.0 ± 5.7 | 24,824 ± 3,281 | 1,128 | 16.3 ± 3.3 | 9,384 ± 797 | 576 |
| AllylCSO | 18.3 ± 4.1 | 64,471 ± 7,569 | 3,523 | 24.1 ± 2.4 | 46,463 ± 2,724 | 1,928 |
| PrenCSO | 2.6 ± 0.5 | 25,085 ± 1,856 | 9,648 | 3.0 ± 0.7 | 21,524 ± 1,867 | 7,175 |
| Cystine | 2.2 ± 0.9 | 30.1 ± 3.0 | 14 | 9.7 ± 3.2 | 35.6 ± 5.9 | 4 |
| Methyl Cys | No activity | No activity | ||||
| Cys | No activity | No activity | ||||
| Cystathionine | No activity | No activity | ||||
Reactions were carried out in vitro in solution. Km and Vmax were calculated using a least-squares-fit method.