Cats, as obligate carnivores, can metabolize high amounts of meat because their argininosuccinate synthase is constantly active.

“so cats are obligate carnivores and so they can eat all that meat that they want they can get around it because our general succinate synthase in cats is not up regulated it's constantly turned on so if they eat a ton of meat then they can metabolize it over the course of a 24 48 hour period whereas we can't”

“so with humans when we go down to low protein diets that enzyme is down regulated when we go to high protein diets that enzyme is up regulated and so we upregulation stops at about 35 maybe 40 percent max of calories”

“35 percent of energy sugar and so 35 percent of energy represents the the average maximal pearl protein ceiling that humans can ingest and so whether your readers know it or not is nitrogen is toxic and so we have to get rid of nitrogen by the liver synthesizing urea and the rate-limiting enzyme for the synthesis of urea is a compound called our jin.o succinate synthetase”

“the thing that's very interesting about humans is that many of these enzymes specifically arginase and arginosuccinase can only be upregulated to a small extent as we increase our protein consumption that is to say that in obligate carnivores things like lions cats felids they can actually upregulate those enzymes infinitely our biochemistry is different we have a ceiling to which we can upregulate those enzymes”