Table 2.

Activation constants of hCA I, hCA II and the bacterial enzymes PhaCA (Pseudoalteromonas haloplanktis) and CpsCA (Colwellia psychrerythraea) with amino acids and amines 1–24, by a stopped-flow CO₂ hydrase assay [42].

No.	Compound	KA (μM) *
		hCA I a	hCA II a	PhaCA b	CpsCA b
1	l-His	0.03	10.9	12.6	47.5
2	d-His	0.09	43	9.41	35.9
3	l-Phe	0.07	0.013	15.8	>100
4	d-Phe	86	0.035	3.19	15.4
5	l-DOPA	3.1	11.4	1.08	4.79
6	d-DOPA	4.9	7.8	0.72	11.2
7	l-Trp	44	27	7.12	21.3
8	d-Trp	41	12	13.9	36.8
9	l-Tyr	0.02	0.011	1.02	19.5
10	d-Tyr	0.04	0.013	7.35	18.4
11	4-H2N-l-Phe	0.24	0.15	3.27	17.2
12	Histamine	2.1	125	6.48	20.6
13	Dopamine	13.5	9.2	8.70	32.1
14	Serotonin	45	50	9.05	34.8
15	2-Pyridyl-methylamine	26	34	2.39	21.5
16	2-(2-Aminoethyl)pyridine	13	15	18.7	38.2
17	1-(2-Aminoethyl)-piperazine	7.4	2.3	15.1	33.0
18	4-(2-Aminoethyl)-morpholine	0.14	0.19	10.1	34.3
19	l-Adrenaline	0.09	96.0	17.5	79.8
20	l-Asn	11.3	>100	9.80	27.9
21	l-Asp	5.20	>100	9.85	27.3
22	l-Glu	6.43	>100	9.01	24.4
23	d-Glu	10.7	>100	4.72	12.0
24	l-Gln	>100	>50	32.4	>100

* Means were obtained from three determinations by a stopped-flow CO₂ hydrase method [42]. Standard errors were in the range of 5–10% of the reported values (data not shown). ^a Human recombinant isozymes, from [35]; ^b Antarctic bacterial recombinant enzyme, this work.