Table 3.
Biochemical comparison of benzenoid carboxyl methyltransferases
| SAMT-type |
BAMT-type |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| H. c. SAMT | P. h. BSMT1 | P. h. BSMT2 | S. f. SAMT | A. m. SAMT | C. b. SAMT | A. t. BSMT | A. l. BSMT | N. s. BSMT | A. m. BAMT | |
| Calculated subunit mass (D) | 41,360 | 40,662 | 40,676 | 41,316 | 43,690 | 40,289 | 43,365 | 43,234 | 39,944 | 41,011 |
| Holoenzyme mass (D) | nd | 78,430 | 77,100 | 70,000 | 107,000 | 74,500 | 91,000 | 91,000 | nd | 100,000 |
| pH optimum | 7.2–7.6 | 7–8 | 6.5–7.5 | 7.0–7.8 | 7–7.5 | 7.5 | 7–8 | 7–8 | 6.8 | 7.5 |
| Temperature optimum (°C) | nd | nd | nd | 10–20 | nd | 20 | nd | nd | 15–20 | nd |
| Salicylic acid (%) | 100 | 100 | 100 | 100 | 100 | 100 | 46 | 16 | 22.5 | 0 |
| Benzoic acid (%) | 10 | 16.3 | 27.3 | 31.9 | 45 | 69 | 100 | 100 | 100 | 100 |
| 3-OH-BA (%) | 0 | 0.65 | 1.32 | 75.6 | 0 | <2 | 54 | 0 | 15.3 | 0 |
| 4-OH-BA (%) | 0 | nd | nd | 34 | 0 | 0 | 0 | 0 | 76.2 | 0 |
| Cinnamic acid (%) | 0 | 0.41 | 0.69 | 34.5 | 0 | <2 | 0 | 0 | 16.5 | 0 |
| o-Coumaric acid (%) | nd | 0.14 | 0.25 | 25.0 | 0 | nd | nd | nd | 21 | 0 |
| m-Coumaric acid (%) | nd | 0.24 | 0.5 | 23.8 | 0 | nd | nd | nd | 4.9 | 0 |
| 2,3-OH-BA (%) | nd | nd | nd | 99.5 | nd | nd | nd | nd | 14.9 | nd |
| 2,4-OH-BA (%) | nd | nd | nd | 98.5 | nd | nd | nd | nd | 18.2 | nd |
| Km (SAM) μM | nd | 1.9–15.8 | 2.8–30.8 | 63 | 3–4 | 9 | 67 | 87 | 2.25 | 28–87 |
| Km (SA) μM | nd | 51.6 | 69.6 | 250 | 83 | 24 | 16 | 127 | 162.2 | no subst |
| Km (BA) μM | nd | 1273 | 2356 | 2900 | 1720 | 190 | 65 | 131 | 148.6 | 1100–1500 |
| Kcat/Km (SA) s−1 M−1 | nd | 230 | 57 | 16.3 | 132 | 116.7 | 4300 | 400 | 160.3 | no subst. |
| Kcat/Km (BA) s−1 M−1 | nd | 3 | 1.4 | 14.6 | 3.37 | nd | 2900 | 9600 | 625.8 | 19–27 |
nd: not determined; no subst: no substrate.