Why don't mammals produce cellulase?

Debate and discussion of any biological questions not pertaining to a particular topic.

Moderators: honeev, Leonid, amiradm, BioTeam

siroma
Garter
Garter
Posts: 32
Joined: Thu Jun 28, 2007 5:31 pm

Why don't mammals produce cellulase?

Post by siroma » Sat Jul 07, 2007 11:57 pm

Hi all!

Of all mammals only ruminants can digest wood. Even they use help of simbiotic bacteria/prostists to prepair dinner for them.
Wood is almost everywhere, storing endless amount of energy. Why don't most animals utilize this energy?

I can bring somewhat awkward explaination: "If most animals could eat wood, there would be no wood. If they could, wood would be consisting not of cellulose, but something that animals cannot digest."

Well, but maybe there is some basic principle which, say, mammals cannot bypass to eat wood?

User avatar
mith
Inland Taipan
Inland Taipan
Posts: 5345
Joined: Thu Jan 20, 2005 8:14 pm
Location: Nashville, TN
Contact:

Post by mith » Sun Jul 08, 2007 6:05 am

very interesting, I haven't thought about this before
Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr

Darby
Viper
Viper
Posts: 1278
Joined: Thu Mar 02, 2006 5:29 pm
Location: New York, USA

Post by Darby » Mon Jul 09, 2007 12:09 pm

Those ruminants can't digest wood - just the less dense cellulose of fiber.

And they use symbionts to do it.

There are almost no animals that digest cellulose with only their own enzymes. It may represent one of the oldest symbioses around.

siroma
Garter
Garter
Posts: 32
Joined: Thu Jun 28, 2007 5:31 pm

Post by siroma » Mon Jul 09, 2007 5:19 pm

Darby wrote:There are almost no animals that digest cellulose with only their own enzymes.


That's it. But why? The process is ineffective? But to digest cellulose an animal seems to have only one additional enzyme, breaking beta(1-4) links to get free, sweet, tasty glucose.

User avatar
MrMistery
Inland Taipan
Inland Taipan
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)
Contact:

Post by MrMistery » Mon Jul 09, 2007 6:10 pm

Only earthworms and some inferior insects can digest cellulose, beacuse they have the enzyme commonly named cellulase. But as we know, chordates are not direct descendents of insects, so the enzyme simply wasn't available to them. It is a very simple principle: evolution does not create something on demand, it has to mold things that arrise randomly. And we can only speculate that in our case, it didn't arrise.
By the way, the main constituent of wood is not cellulose, but lignin. Lignin is a branched polymer made out of some phenolic monomers, derived from the aminoacid phenylalanine.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

siroma
Garter
Garter
Posts: 32
Joined: Thu Jun 28, 2007 5:31 pm

Post by siroma » Tue Jul 10, 2007 11:02 am

MrMistery wrote:evolution does not create something on demand, it has to mold things that arrise randomly.


That's right. But is absence of cellulase enzyme only due to "bad" luck of gene generation, in which the enzyme didn't arise randomly, or are there some other, more fundamental limitations, for example, ineffectiveness of cellulose digestion process that cannot supply enof energy for, say, mammals?

Darby
Viper
Viper
Posts: 1278
Joined: Thu Mar 02, 2006 5:29 pm
Location: New York, USA

Post by Darby » Wed Jul 11, 2007 3:18 pm

It may just be the path of least resistance - just as we humans don't make coenzymes already available in our ancestral diet, why would animals derive a huge advantage from developing an enzyme that well-adapted symbionts already have and use to the host's advantage?

User avatar
MichaelXY
King Cobra
King Cobra
Posts: 885
Joined: Fri Jun 15, 2007 7:03 pm
Location: San Diego, Ca

Post by MichaelXY » Sat Jul 14, 2007 7:07 am

Would it be possible for animals to be given a cellulase tablet, thereby enabling one to ingest cellulose?
Kinda like they do for those that are lactose intolerent.

Ultrashogun
Coral
Coral
Posts: 149
Joined: Wed Jan 04, 2006 4:48 am

Post by Ultrashogun » Sun Jul 15, 2007 2:50 am

Because its much easier to just make a sammich than evolve a new enzyme.

siroma
Garter
Garter
Posts: 32
Joined: Thu Jun 28, 2007 5:31 pm

Post by siroma » Mon Jul 16, 2007 4:16 pm

Sammich? What do you mean?

User avatar
kotoreru
Coral
Coral
Posts: 400
Joined: Thu Apr 12, 2007 9:25 pm
Location: London

Post by kotoreru » Mon Jul 16, 2007 6:53 pm

I think he needs 'sandwich', dear...
"What are humans if they don't learn at University? Animals, yes."

^^One of my ex-girlfriends said that. I stress the ex part.

siroma
Garter
Garter
Posts: 32
Joined: Thu Jun 28, 2007 5:31 pm

Post by siroma » Mon Jul 16, 2007 7:54 pm

Oh! That's profound suggestion.

Post Reply

Who is online

Users browsing this forum: ethfggnde and 25 guests