ABSTRACT
Mycophenolic acid (MPA, ) and its derivatives are first-line immunosuppressants used in organ transplantation and for treating autoimmune diseases. Despite chemical synthetic achievements, the biosynthetic formation of a seven-carbon carboxylic acid pharmacophore side chain of , especially the processes involving the cleavage of the prenyl side chain between DHMP () and DMMPA (), remains unknown. In this work, we identified a membrane-bound prenyltransferase, PgMpaA, that transfers FPP to to yield FDHMP (). Compound undergoes the first cleavage step a new globin-like enzyme PgMpaB to form a cryptic intermediate . Heterologous expression of genes in demonstrates that the second cleavage step (from to ) of is a cluster-independent process . Our results, especially the discovery of the broad tolerance of substrates recognized by PgMpaB, set up a strategy for the formation of "pseudo-isopentenyl" natural products using fungal globin-like enzymes.
ABSTRACT
A new sesquiterpene hydroquinone (1) was isolated from a deep sea sediment derived fungus, Phialocephala sp.. Its structure and stereochemistry were established on the basis of spectroscopic data and optical rotation. This compound was tested for cytotoxicity against P388 (murine leukemia cell) and K562 (human leukemia cell) cell lines, and displayed strong cytotoxic effects with IC50 value of 0.16 and 0.05 micromol x L(-1), separately.