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B.
Shortening an industry’s supply chain is bound to affect the activities of existing suppliers. That is as true of the
recreational-drugs industry as it is of any other. Some street pharmaceuticals, such as methamphetamine and cannabis, are
already made near their main consumer markets—whether manufactured in laboratories or grown under cover in neighboring
countries. But others, particularly cocaine and heroin, still have to be imported from far-flung places where the plants which
produce them flourish in the open. If these internationally traded commodities could be produced locally, the cartels that now
smuggle them might find themselves out of business. Savvy drug barons will therefore be reading their copies of Nature
Chemical Biology with particular interest—for the current edition of the journal contains a paper describing a technology that
could completely disrupt their business models. It may, to be fair, also change the businesses of legitimate drug companies. For
the authors of this paper, John Dueber of the University of California, Berkeley and his colleagues, have found the last piece of
a jigsaw puzzle that will permit opiates to be made from glucose through the agency of yeast. They have still to fit it with the
other pieces, to form a single picture. But when they do so, which is likely to be soon, instead of fermenting sugar into alcohol,
you will be able to ferment it into morphine—and into many other pharmacologically active molecules as well. The path from
glucose, the common currency of biochemistry, to morphine is a long one. In the poppies that produce the stuff naturally (it is
useful because it confuses the nervous systems of potential pests) that pathway has 15 steps, each requiring a particular
enzyme. Several groups of researchers have replicated the later stages of this pathway in yeast, by borrowing appropriate
enzymes (or, rather, the genetic material that encodes them) from poppies, and also from bacteria. These investigators have not,
however, been able to backtrack in yeast beyond a molecule called S-reticuline, which is the hub of the process, in that it can
act as the precursor for many morphine-like substances. The best they have done is to assemble the bit of the pathway that
leads from glucose to S-reticuline, not in yeast but in E. coli, a bacterium.
【題組】43. Which of the following is the key to backtracking?
(A) E. coli. (B) glucose (C) enzymes (D) poppies
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