TABLE 2.
Vmax values of h5-LOX, h12-LOX, and h15-LOX-1 with DHA, 14S-HDHA, 14S-HpDHA, 7S-HDHA, and 7S-HpDHA
| Enzyme | Substrate | Vmax (mol/sec−1/mol−1) | 7S,14S-diHDHA Biosynthetic Pathway Fluxa |
| h5-LOX | DHA | 0.14 ± 0.03 | 0.073 |
| 14S-HDHA | 0.00038 ± 0.0002 | 0.00038 | |
| 14S-HpDHA | 0.0015 ± 0.0006 | 0.0015 | |
| h12-LOX | DHA | 12 ± 1 | 9 |
| 7S-HDHA | 2.8 ± 0.2 | 2.3 | |
| 7S-HpDHA | 0.53 ± 0.08 | 0.44 | |
| h15-LOX-1 | DHA | 0.84 ± 0.09 | 0.34 |
| 7S-HDHA | 1.9 ± 0.1 | 1.7 | |
| 7S-HpDHA | 0.30 ± 0.4 | 0.19 |
Values determined at 10 μM substrate concentration. The Vmax for h5-LOX was approximated by determining the amount of h5-LOX in the ammonium sulfate pellet by Western analysis relative to a known standard. Reactions with DHA represent the first step of the two biosynthetic steps, such as h15-LOX-1 Vmax × percent 14S-HDHA, while reactions with oxylipins represent the second step of the two biosynthetic steps, such as h15-LOX-1 Vmax × percent 7S,14S-HDHA.
a
Biosynthetic flux is calculated by multiplying each Vmax by the percentage of total product from that reaction that serves as substrate for the next step toward synthesis of 7S,14S-diHDHA.