| | 1 | Author
| PaulL D Urham, JonathanE. Poulton | Requires cookie* | | | Title
| Enzymic Properties of Purified Myrosinase from Lepidium sativum Seedlings  | | | | Abstract
| To establish the substrate specificity o f the thioglucoside glucohydrolase myrosinase (EC 3.2.3.1), this enzyme was purified to homogeneity from light-grown cress (Lepidium sativum L.) seedlings by Sephadex gel filtration. Red Dye and anion exchange (FPLC M ono Q) chro matography, and preparative isoelectric focusing. Hydrolytic activity was shown toward only 4 o f the 29 synthetic and natural O-and S-glycosides tested. Highest activity was displayed with the endogenous glucosinolates benzylglucosinolate (ATm, 295 |iM) and sinigrin (K ml 300 |iM) at an optimum pH o f 5.5 in sodium citrate buffer. The synthetic glycosides PNPG (K m, 2.0 m M) and ONPG were poorer substrates at an optimum pH o f 6.5 in potassium phos phate buffer. The enzyme was inactive with all other nitrophenyl glycosides tested including PNP-a-D-glucoside and PNP-thio-ß-D-glucoside, suggesting a requirement for O-ß-D-glucose as the glycone moiety within these substrates. PNPG hydrolysis was stimulated 2.6-fold by ascorbate (1 m M). The enzyme exhibited no metal ion requirement and was strongly inhibited by lead nitrate, mercury chloride, and ferric chloride at 1 m M concentration. The metal chela tors D IE C A , ED TA , o-phenanthroline, and 2,2'-dipyridyl were not inhibitory, but the thiol reagents PCM S, PCMB, and N-ethylmaleimide (at 1 m M) caused 5 0 -8 0 % inhibition o f enzyme activity. | | | |
Reference
| Z. Naturforsch. 45c, 173—178 (1990); received September 9 1989 | | | |
Published
| 1990 | | | |
Keywords
| Lepidium sativum, Thioglucoside Glucohydrolase, M yrosinase, Substrate Specificity, Gluco-sinolate Degradation | | | |
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| ZNC-1990-45c-0173 | | | | Volume
| 45 | |
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