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Tuesday, January 09, 2007

The Smell of Cat Pee

 
Most mammals have a keen sense of smell. That's why urinary odorants and pheromones are used to attract mates and mark territory. In most cases we can't detect these odors but there's one major exception.

The urine of cats contains chemicals that are easily detectable by humans. The smell is not pleasant. Mature cats will spay almost anything to stake out their territory, especially males). This isn't a problem if it's outdoors but it can be a major problem for indoor cats because carpets and spraying are not a good mix.

The urine of mature cats contains a chemical known as felinine (2-amino-7 -hydrozxy-5, 5-dimethyl-4-thiaheptanoic avid). Felinine excretion is stimulated by the hormone testosterone, which isn't produced until the cat reaches maturity. Both male and female cats excrete felinine in their urine but males typically excrete twice as much.

Felinine is odorless, to us. A recent paper (October 2006) describes how it is made and how it is converted to more pungent compounds.

The biochemical pathway leading to felinine begins with 3-methylbutanol- glutathionine (3-MBG) (compound A in the figure below). 3-MBG is a normal precursor in the synthesis of cholesterol but in cats some of it is converted to 3-methylbutanol-cysteinylglycine (3-MBCG) (compound B) by a pepdidase activity that removes glutamate. This reaction takes place in the bloodstream and 3-MBCG is excreted in the urine in cats of from the time they are born.

Mature cat urine contains high levels of protein, 90% of which is a medium-sized protein (70kDa) called cauxin. Cauxin levels rise as the cats reach maturity because transcription of the gene is stimulated by sex hormones. Cauxin is produced only in kidney cells and is secreted directly into the urine. The novel finding is that cauxin is a peptidase that cleaves 3-MBCG producing felinine (compound C). What this means is that production of felinine from 3-MBCG takes place in urine, probably in the nephrons before urine is released into the bladder.

Felinine breaks down into a number of smaller compounds that give rise to the characteristic smell of cat urine. The main breakdown product is 3-mercapto-3-methy-1-butanol formed by splitting felinine at the sulfur atom. Other breakdown products are formed. The complex mixture of derivatives is probably produced by a combination of unknown enzymatic act ivies and spontaneous reactions. The characteristic odor of domestic cats differs from that of lynx and bobcats and the differences are due to the concentrations of the various breakdown products of felinine.
Miyazaki, M., Yamashita, T., Suzuki, T., Saito, Y., Soeta, S., Taira, H., and Suzuki, A. (2006) A Major Urinary Protein of the Domestic Cat Regulates the Production of Felinine, a Putative Pheromone Precursor. Chemistry & Biology 10: 1071-1079.

3 comments :

Monado said...

Nice! Now you can add the logo for blogging about pee-r-reviewed papers.eckkt

donatakb said...

I just read this interesting article online and had a question. Article said that mature cat's urine contains felinine which excresion is stimulated by the testosterone. Question: if the cat is neutered, will cat's urine still contain felinine or not anymore? Thanks!

Nabil said...

One of my 2 cats (both neutered males) had taken to painting all of my walls, furniture, and anything else he could reach. I was horrified when I got a UV light. He never did that in all of the 9 years I've had him and didn't when I got him a buddy (they love each other and did so right away) but when a strange black cat started showing up outside both of my cats went nuts and the older one (9) started his wall painting, as well as the curtains out in the kitty room. I couldn't keep up with it.

My cats are indoor cats so it's not like the stray is actually going to get in here but they both hate him (and he is weird...my neighbor's cats hate him too). I've tried cleaning with a pet urine enzyme and then spraying some "No More Spraying" but that hasn't worked. He's a sneaky little bugger too; he waits until he thinks I'm not looking and then does it. He's learned that the minute I see him backing his butt up to something he gets yelled at.

It wasn't until I found "Cat Spraying No More" that I was able to finally get rid of this tiresome behavior.

Now my house doesn't smell like a litter box anymore :)

Here's a link the their site if you're interested in checking out: http://nomorecatpee.com