The role of the C8 proton of ATP in the catalysis of shikimate kinase and adenylate kinase

BMC Biochemistry

Table 2 Steady state specific activities of SK and AK1, WT and mutant enzymes

Enzyme	SK		AK1A		AK1B
Enzyme	Residue	Specific activity ¹	Residue	Specific activity	Residue	Specific activity
1. Wild type	WT	101,89	WT	110
2. Thr-C8H	T17I	16.73	T23V	250	T39V	19.54
3.	T17R	4.93
4. Arg-C8H	R110A	0.92	R128A	0.128	R97A	2.61
5.			R128Q	<1	R97Q	<1
6.			R128K	<1	R97K	<1
7. Arg-α/β-PO₄	R117	ND	R132A	0.28	R44	ND
8.			R132K	1.08
9.			R132Q	0.00
10. Lys- γ-PO₄	K15I	1.665	K21	ND
11.	K15R	0.386

¹ umoles/mg protein/min.
SDM of amino acid residues making up the “push” mechanism within the active sites of SK and AK1. These residues included: the Thr associated with the proton transfer from C8-H to the α-PO₄ (SK, Thr17; AK1, Thr 23), the Arg associated with C8 protonation (SK, Arg110; AK1, Arg128), the Arg co-ordinated to the α-PO₄ and β-PO₄ (SK, Arg117; AK1, Arg132), and the Lys associated with the γ-PO₄ protonation (SK, Lys15; AK1; Lys21). The residues identified in the AK1 second nucleotide binding site (AK1B) are: Thr 39 (associated with the proton transfer from C8H to the α-PO₄), Arg 97 (associated with C8 protonation), Arg44/138 (co-ordinated to the α-PO₄ and β-PO₄, and Lys21 (associated with the γ-PO₄ protonation).

ISSN: 1471-2091