Identification and Partial Characterization of an L-Tyrosine Aminotransferase (TAT) from Arabidopsis thaliana

Table 2

(a) Kinetic properties of At5g36160. The enzyme assays used to determine the kinetic parameters are described in Section 2. 𝐕_max is represented in 𝜇moles min^-1 mg^-1 of protein, 𝐾_𝑚 of the various substrates is represented in millimolar (mM), and 𝐾_cat is represented in S^-1. The measurements were made under optimal conditions with respect to pH, temperature, and substrate concentrations (supplementary material). The kinetic constants were calculated by nonlinear regression analysis using the GraphPad Prism Version 3.03 software. (b) Relative substrate specificity of At5g36160 with various amino acceptors. The assay measured the production of 4-hydroxyphenylpyruvate at 331 nm using 10 mM amino donor (L-Tyrosine) and 10 mM amino acceptor.

(a)

Assay	𝑉max	𝐾cat	Substrate	𝐾𝑚
Forward	5±0.3	0.08	L-Tyrosine	0.19±0.16
			L-Phenylalanine	0.84±0.2
			2-ketoglutarate	1.2±0.27
Reverse	23.5±1.0	6.1	L-Glutamate	1.4±0.16
			4-hydroxyphenylpyruvate	0.22±0.05
			Phenylpyruvate	0.13±0.06

(b)

Acceptor/Donor combinations	Relative Activity (%)
L-Tyrosine/2-ketoglutarate	100
L-Tyrosine/oxaloacetate	75
L-Tyrosine/pyruvate	40
L-Tyrosine/prephenate	23
L-Tyrosine/oxovalerate	3