Table 1.
Comparative biochemical characteristics of the four tegumental ectoenzymes that are known to control the S. mansoni purinergic halo.
| SmATPDase1 | SmNPP5 | SmNACE | SmAP | |
|---|---|---|---|---|
| Size (AA#) | 544 | 458 | 303 | 536 |
| Mol Mass (Da) | 61,353 | 52,563 | 34,758 | 59,375 |
| pI | 9.11 | 6.28 | 7.13 | 5.92 |
| GPI-linked | − | + | + | + |
| Glycoprotein | ? | + | + | + |
| pH optimum (range) | ATP: 8.5–10 ADP: 7.5–10 |
ATP: 8–8.5 ADP: 7–10 |
ATP: 7–8 ADP: 7–10 |
ATP: 9 ADP: 8–10 |
| Cation requirement | Ca≥Mg | Mg=Ca=Zn | None | Mg >>Ca>Zn>Cu |
| Substrates (K m , μM±SD) | ATP (400 ±20) ADP (252 ±20) |
NAD (200 ±0.6) ATP (217 ±26) ADP (246 ±34) ADPR |
NAD (49 ±3.5) NADP (14 ±2.9) NDG (23 ±1.1) NMN (1084 ±164) |
AMP (650 ±22) CMP (630 ±20) GMP (640 ±11) TMP (595 ±33) pNPP (288 ±12) polyP (6900 ±1000) S1P, PLP |
| Accession# | AY323529 | EU769293 | AAX35328 | EU040139 |
| References | [23, 24] | [25, 26–28, 40] | [35, 40, 45] | [29, 30, 53, 56, 57] |
Km values reported here were measured at each enzyme’s optimal pH. Whether SmATPDase1 is glycosylated is unknown, indicated by “?”. GenBank accession numbers for each enzyme are listed. AA#: amino acid number, Mol Mass (Da): Molecular Mass (Daltons), pI: isoelectric point. The full designations of most listed substrates are given in Figure 1. NADP, nicotinamide adenine dinucleotide phosphate; NGD, nicotinamide guanine dinucleotide; pNPP p-nitrophenyl phosphate; polyP, polyphosphate; S1P, sphingosine-1-phosphate; PLP, pyridoxal phosphate.