Oct. 10, 2000 TOWNSVILLE, Queensland, Aust.--Researchers may have solved part of a puzzle of the sea: where does all the chitin go--the substance that makes up all the shells of crabs, lobsters and shrimp and other crustaceans?
Chitin may be the most abundant natural compound in the sea with estimates of up to 10 million metric tons alone in tiny crustaceans called krill. However, scientists have not yet found a sufficient natural sink, an endpoint where all the chitin goes.
At the International Marine Biotechnology Conference today, Cassandra M. Moe reported finding an enzyme in the gut of rainbow trout, Onchorynchus mykiss that degrades chitin. Moe, a graduate research assistant, and colleagues at the University of Maryland Biotechnology Institute's Center of Marine Biotechnology (COMB) have identified the chitinase in a wide range of vertebrate species of fish, birds, reptiles and mammals.
It is the first gastric chitinase reported characterized in vertebrate animals, said Moe.
In the COMB tests on vertebrate animals, rainbow trout, which feeds mostly on insects, showed the highest amounts of the chitinase in the gut, said Moe. But there is an odd twist to the story. Little of the chitin that passes through the trout gut actually gets digested.
"Based on our findings, we think chitinase may be an ancient gastric enzyme that may be pathogenic, attacking fungi or bacteria, instead of being a digestive enzyme. It is not a product of the gut flora," said Moe. She added that scientists in The Netherlands have found chitinase in human macrophages, immunity cells in the blood, probably as a defense against microbial invaders.
The COMB researchers have purified the chitinase from the gastric tissues of the rainbow trout. Moe said in the trout the enzyme may also act as "a food processor" to break chitin away from cuticles that hold skeletal tissues in place on the prey they eat.
Chitin is also abundant in fungi, worms, spiders, insects and some algae. It is the second most common natural product on Earth after cellulose.
COMB, in Baltimore, Md. USA, is one of five centers of the University of Maryland Biotechnology Institute, a unique life sciences research and education arm of the University System of Maryland. One of UMBI's first two research centers founded in 1985, COMB has achieved international recognition as a center of excellence in the study, protection and enhancement of marine resources.
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