Chemists pin down poppy's tricks for making morphine Identifying enzymes involved in opiate synthesis could mean better ways to make painkillers
By Rachel Ehrenberg
Web edition : Sunday, March 14th, 2010
Opiates for the masses may not be far off. Scientists have figured out two of the final steps in the chain of chemical reactions that synthesize
morphine in the opium poppy.
Pinpointing the cellular workhorses and the genes involved in making morphine may lead to new production methods for the drug and its chemical cousins
such as codeine, oxycodone and buprenorphine, scientists report in a paper published online March 14 in Nature Chemical Biology.
Morphine and its relatives, widely used as painkillers in developed countries, are fairly expensive and are often taken for extended periods of time.
The new research may lead to better ways of engineering yeast or other microbes to make these painkillers — perhaps skirting the social and
political morass of agricultural poppy production, the source of heroin.
“Moving production of morphine and its metabolites such as codeine into a microbial system — if you could get yields up — could help lower
costs,” says bioengineer Christina Smolke of Stanford University, who was not involved in the research. Instead of having to purchase these opiates
from other nations, “maybe countries could even do local synthesis,” she says.
The new work identifies two enzymes — the proteins that cells use to build molecules and make reactions go — involved in turning the chemical
precursors thebaine and codeine into morphine. Study coauthors Jillian Hagel and Peter Facchini of the University of Calgary in Canada also pinpointed
the genes encoding each enzyme and verified this genetic role with poppy plant experiments.
“This is really terrific work,” says Philip Larkin, head of the plant product metabolic engineering program at Australia's national science agency
CSIRO in Canberra. “Having these genes in the hand gives you much greater versatility.” For example, scientists could engineer high-yield plants
by cranking up the activity of the morphine synthesis genes, Larkin says.
Scientists could also block morphine production with engineered viruses that shut down the genes. In theory, such viruses might be used to eradicate
opium poppy crops in places such as Afghanistan. But narcotic control experts question the wisdom of such a maneuver.
“There are formidable tactical obstacles that would have to be addressed,” says Charles S. Helling, former senior scientific advisor to the State
Department’s Bureau of International Narcotics and Law Enforcement Affairs. “But the even bigger problems are political,” he adds. “It’s a
very difficult situation that is further complicated by the military situation.”
Morphine is an alkaloid, a class of compounds characterized by a ringed molecular structure incorporating a bit of nitrogen. “Among all the natural
products, alkaloids tend to display the most potent pharmacological effects,” Facchini says. Plants produce roughly 12,000 kinds of alkaloids,
including nicotine, strychnine, caffeine, mescaline, quinine and atropine.
A handful of very old plant groups, including the poppy and buttercup families, produce the class of alkaloids that morphine belongs to, called
benzylisoquinoline alkaloids. The main building block for the roughly 2,500 alkaloids in this class is the amino acid tyrosine. A 15- to 20-step
reaction pathway turns tyrosine into morphine. While questions remain about some of the very early reactions, pinning down the final morphine
production steps is the key to unlocking a host of practical applications.
Years of research, gift plants, a bit of luck and the “Herculean effort” of then graduate student Hagel led to the discovery, says Facchini.
The researchers began with three high-morphine varieties of opium poppy, Papaver somniferum, and a mutant plant that makes the morphine precursors
thebaine and oripavine but can’t make morphine itself. Hagel constructed an enormous DNA library from these plants, which the team used to determine
which genes were turned on in the morphine-making poppies. She then compared this activity to that of the mutant plant that couldn’t put morphine
together.
After determining the genetic blueprints of the genes that differed, Hagel and Facchini checked those DNA sequences against a database to reveal the
enzymes’ identities. To verify the enzymes’ role in making morphine, Hagel stuck one of the genes into the bacterium E.coli, put the critter in a
flask with some thebaine, and left it overnight.
“When she came back the next morning, the thebaine was all gone,” says Facchini. “That’s when her eyes got big…. Finding it all had been
turned into morphine — that gives a grad student a great sense of power, when they can make morphine.” The scientists dubbed the enzymes thebaine
6-O-demethylase and codeine O-demethylase.
Both of the newly identified enzymes are in charge of the same structural task — removing a methyl group, a common chemical ornament comprising a
carbon and three hydrogen atoms. But in the hunt for these morphine-synthesis enzymes, many scientists were led astray. There was an assumption that
poppies used a methyl-removing enzyme similar to the one that the human liver uses to remove methyl groups. But poppies use enzymes from an entirely
different class, the researchers report.
“These are enzymes that have eluded discovery for a long time,” says MIT biochemist Sarah O'Connor. And they turned out to be enzymes that
weren’t really on the radar. “In plants, it’s very hard to figure out the enzymatic steps of a pathway,” she notes. “This is a beautiful
example of how you can use modern molecular biology tools to solve this problem.” JohnWW - 15-3-2010 at 23:42
That is very interesting news, for professional chemists and biochemists, pharmacists, - and druggies. This research could also be used to induce
species of poppy (Papaver and some related genuses) other than the opium poppy, Papaver Somniferum, which produce much smaller quantities of morphine
and related alkaloids and often produce large amounts of papaverine (which is also the active ingredient of pepper, from Piper and Macropiper species)
and other non-morphine ones instead, to produce greatly increased amounts of morphine alkaloids (mostly morphine and codeine).
It is also to be note that natural morphine alkaloids are also phenylethylamine derivatives, like amphetamines, but the latter have a quite different
physiological effect. The "morphine rule", for opioid analgesic physiological effects accompanied by various levels of addictiveness, is: an aromatic
ring, attached to a quaternary carbon, attached to 2 or more carbons, attached to a tertiary amine nitrogen; i.e. C6H5-C(-C)(-C)-C-C-N(-C)(-C). This
has resulted in the synthetic discovery of simpler molecules which obey the morphine rule, having similar analgesic effects while being much less
addictive, and not all of which are also phenylethylamine derivatives. Thus methadone, meperidine, and dextromethorphan (used in cough remedies) are
simpler molecules that obey the morphine rule; but of these, only dextromethorphan is also a phenylethylamine derivative.
BTW I have just uploaded to my Rapidshare premium account an important classic ebook on this subject, which has been out-of-print for many years, and
which appears to be much sought-after because of the numerous references to it in the scientific literature: The Chemistry Of The Morphine Alkaloids, by K W Bentley (Oxford-1954).
The link for downloading it is in the Organic Chemistry books thread in the references section, although it is out-of-copyright in many countries
including mine; or I could give it to you privately.
BTW: This thread should, more appropriately, be in either the Organic Chemistry or the Biochemistry sections.
[Edited on 16-3-10 by JohnWW]Magpie - 16-3-2010 at 12:13
This just amazes me how excited the legitimate users of morphine are about facilitating its production. One would hope that the DEA and LEO are
equally unexcited. If the legitimate users want domestic morphine so badly why don't we just grow poppies. I'm sure our farmers would be glad to
grow this high profit crop, under proper restrictions, of course.
Quote:
Plants produce roughly 12,000 kinds of alkaloids, including nicotine, strychnine, caffeine, mescaline, quinine and atropine.
Talk about job security for the DEA.Polverone - 16-3-2010 at 12:47
This just amazes me how excited the legitimate users of morphine are about facilitating its production. One would hope that the DEA and LEO are
equally unexcited. If the legitimate users want domestic morphine so badly why don't we just grow poppies. I'm sure our farmers would be glad to
grow this high profit crop, under proper restrictions, of course.
The Opium Poppy Control Act of 1942 prohibits the domestic growing of poppies for production of morphine or other drugs, even for legal medicinal use,
unless insufficient import sources are available. American farmers aren't going to get a crack at the market unless all the foreign producers give up
simultaneously.
Speaking of foreign producers, there is another weird quirk: imported raw materials for narcotic production (poppy straw, etc.) must be 80% sourced from Turkey or India unless shortages make it
impossible. So even if higher-tech producers operating in nations like Spain, France, or Australia can beat Turkish and Indian producers on efficiency
or price they're allowed only a small slice of the American market.
Maybe the prospect of biotech-alkaloids is exciting to producers because it bypasses these poppy-specific restrictions. That's hinted at in this
quote:
Quote:
“Moving production of morphine and its metabolites such as codeine into a microbial system — if you could get yields up — could help lower
costs,” says bioengineer Christina Smolke of Stanford University, who was not involved in the research. Instead of having to purchase these opiates
from other nations, “maybe countries could even do local synthesis,” she says.
[Edited on 3-16-2010 by Polverone]JohnWW - 16-3-2010 at 15:49
I note that the above article says:
"A handful of very old plant groups, including the poppy and buttercup families, produce the class of alkaloids that morphine belongs to, called
benzylisoquinoline alkaloids. The main building block for the roughly 2,500 alkaloids in this class is the amino acid tyrosine. A 15- to 20-step
reaction pathway turns tyrosine into morphine. While questions remain about some of the very early reactions, pinning down the final morphine
production steps is the key to unlocking a host of practical applications."
I have heard somewhere of large doses of tyrosine, which is para-HO-C6H4-CH2-CH(NH2)-C(=O)OH (but which of the two enantiomers, only one of which
would occur naturally?) being added to fertilizers used on opium poppy plants to greatly increase their yield of morphine and codeine. Presumably this
could also be tried, perfectly legally, on OTHER species of wild or cultivated poppy, such as the California desert poppy or the European field poppy
(seeds of which can be bought in plant shops), to induce them to produce greatly increased amounts of morphine alkaloids. It could also be tried on
wild buttercups, which are a very common weed here in New Zealand, noting also that the strawberry is a cultivated species of buttercup. So the task
of the U$ DEA is IMPOSSIBLE!
Besides dosing the plants with tyrosine, I daresay that phenylalanine, C6H5-CH2-CH(NH2)-C(=O)OH , may also be useable for the purpose, although the
biosynthesis of that to morphine would additionally require an -OH group to be added to the ring, para to the chain with the N atom. In both cases, in
metabolism to morphine, the N atom would have to be biochemically converted from a primary to a tertiary amine, which usually requires electrophilic
addition of carbocations then loss of H+. Both amino-acids (the naturally-occurring enantiomers) can be bought OTC at health supplements stores, so I
understand.
[Edited on 17-3-10 by JohnWW]bquirky - 16-3-2010 at 21:17
If i was that guy with the opiate craping bugs.. id be very careful.. there would be quite a few people keen to get or prevent others from getting
such things..The_Davster - 16-3-2010 at 22:22
