Table II.

Kinetic constants of mutated CH3 and SHT proteins with tyramine and serotonin as amine substrates

Feruloyl-CoA (250 μm) was used as the acyl donor. ND, Not detected.

EnzymeTyramineSerotonin
KmVmaxVmax/KmKmVmaxVmax/Km
μmnkat mg−1μmnkat mg−1
CH316,6589.40.00052,36027.00.0114
CH3-S153N28,00019.10.00073,78919.10.0050
CH3-L156C27,90030.10.00112,38216.30.0068
CH3-G158Y25,80032.20.00127,00614.80.0021
THT4066.81.6750NDNDND
THT-SLG17,0009.00.0005NDNDND
SHT1,16517.00.0146736.50.0890
SHT-S153N1,32555.30.04171299.10.0705
SHT-L156C1,73940.80.0234446.60.1500
SHT-G158Y14,9515.10.000319,87629.40.0015
SHT-NCY31,5417.20.00027,54615.70.0020
SHT-Y149F16015.50.09681,5137.50.0049
SHT-F151Y7837.60.00974505.80.0128
SHT-FY1,3705.80.00424,0514.00.0010