Dehydrocyclopeptine epoxidase

Fig. 5. Biosynthetic pathway to cyclopenin and cyclopenol (37). Enzyme activities involved (I) cyclopeptine synthetase (2) cyclopeptine dehydrogenase (3) dehydrocyclopeptine epoxidase (4)...

The highest specific activity of dehydrocyclopeptine epoxidase was measured after acetone treatment of hyphal cells and conidiospores. More than one-third of the measurable activity sedimented with the cell wall-plasma membrane fraction, from which it could be solubilized by a 1% solution of deoxycholate. The soluble enzyme fraction was purified by ammonium sulfate precipitation and gel chromatography, and its molecular weight was estimated to be near 500,000. 

Fig. 10. In vitro activities of the enzymes of alkaloid biosynthesis and rates of alkaloid formation in hyphae of Penicitlium cyclopium (75). Cultivation conditions were as described in the legend to Fig. 9. At the times indicated by arrows, cycloheximide (100 p.g/ml) was added to the culture medium. All values are in units per 1 cm of culture area. (A) Anthranilate adenylyltransferase (AA) (100 = 5.6 pkat) ( ) cyclopeptine dehydrogenase (CD) (100 = 40 pkat) ( ) dehydrocyclopeptine epoxidase (DE) (100 = 0.42 pkat) (A) cyclopenin m-hydroxylase (CH) (100 = 12 pkat) (O) cyclopenin-cyclopenol formation in vivo (100 = 9 pmol/sec).

C olopeptine synthetase complex, (2) oyolopeptine dehydrogenase, (3) dehydrocyclopeptine epoxidase,... 

Figure 3.61 Biosynthetic pathway to cyclopenin and cyclopenol, and their conversion to viridicatin and viridicatol, respectively, in Penicillium cyclopium. (i) cyclopeptinsynthase complex (ii) cyclopeptin dehydrogenase (iii) dehydrocyclopeptin epoxidase (iv) cyclopenin m-hydroxylase (v) cyclopenase.

Enzymes of alkaloid biosynthesis are induced in a coordinated manner by an internal signal during development of the mold. However, the rates of alkaloid production increase later than enzyme activities, The increase of both processes can be stopped by addition of inhibitors of gene expression, e.g., 6-fluorouracil or cycloheximide (cf. arrows), indicating that alkaloid production is controlled by the formation of a protein which is not an enzyme of alkaloid biosynthesis. Ordinate relative values A A anthranilic acid adenylyl transferase (a) CD cyclopeptine dehydrogenase (v) DE dehydrocyclopeptine epoxidase ( ) CmH cyclopenin m-hydroxvlase (A)... 

Cyclopeptine synthetase 2 cyclopeptine dehydrogenase 3 dehydrocyclopeptine epoxidase 4 cyclopenin m-hydroxylase 5 cyclopenase... 

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