Table 2.

Activation constants of hCA I, hCA II and the bacterial β-CAs investigated here with amino acids and amines 1–24, by a stopped-flow CO₂hydrase assay ²⁰ .

No.	Compound	KA (μM)a
		hCAI b	hCAII b	BsuCA1 c	FtuCAc
1	L-His	0.03	10.9	1.76	40.7
2	D-His	0.09	43	12.3	78.3
3	L-Phe	0.07	0.013	1.16	69.1
4	D-Phe	86	0.035	1.21	75.0
5	L-DOPA	3.1	11.4	2.07	>100
6	D-DOPA	4.9	7.8	2.34	44.8
7	L-Trp	44	27	1.25	34.1
8	D-Trp	41	12	13.7	30.5
9	L-Tyr	0.02	0.011	1.38	>100
10	D-Tyr	0.04	0.013	0.95	>100
11	4-H2N-L-Phe	0.24	0.15	1.18	>100
12	Histamine	2.1	125	3.71	>100
13	Dopamine	13.5	9.20	1.54	>100
14	Serotonin	45	50	4.26	>100
15	2-Pyridyl-methylamine	26	34	1.62	46.3
16	2-(2-Aminoethyl)pyridine	13	15	5.20	>100
17	1-(2-Aminoethyl)-piperazine	7.4	2.30	43.1	51.8
18	4-(2-Aminoethyl)-morpholine	0.14	0.19	9.56	>100
19	L-Adrenaline	0.09	96	0.70	>100
20	L-Asn	11.3	>100	7.38	>100
21	L-Asp	5.20	>100	6.82	>100
22	L-Glu	6.43	>100	9.36	9.13
23	D-Glu	10.7	>100	1.39	>100
24	L-Gln	>100	>50	3.21	45.7

^aMean from three determinations by a stopped-flow, CO₂ hydrase method ²⁰ . Standard errors were in the range of 5–10% of the reported values (data not shown).

^bHuman recombinant isozymes, stopped flow CO₂ hydrase assay method ²⁶ .

^cBacterial enzyme, this work.