A mer dalej swoje głupotki płodzi. Ale rozumiem, efekt Krugera-Dunninga, jak się czegoś nie rozumie to się przyjmuje wiadomości tak jak pasują do światopoglądu etc. etc. .
Considering that amphibians eat chitin-covered preys, it is highly probable that chitinolytic enzymes would be required for the digestion of the ingested animals. In fact, Micha et al. (1973) demonstrated chitinase activity in the gastric mucosa and pancreas of 4 species of amphibians, i. e., Rana temporaria, Bufo marinus, Salamandra salamandra taeniata and Triturus alpestris alpestinus. However, it was only very recently that the isolation and molecular characterization of an amphibian chitinase was done. We isolated from the pancreas of the toad Bufo japonicus a 60-kDa protein possessing a potent chitinase activity with a considerable amino acid sequence homology (about 50%) with known mammalian chitinases (Oshima et al., 2002). Using a cDNA encoding this chitinase as a probe, we found the mRNA for this enzyme to be expressed exclusively in the pancreas. We designated this chitinase as toad pancreatic chitinase (tPCase). The optimum pH of tPCase was 6.0.
On the other hand, we noticed that a crude extract of the stomach from the same species exhibited chitinase activity (unpublished data), indicating that another chitinase, perhaps different from tPCase, exists in the stomach of the toad. In the present experiment, we obtained a cDNA clone encoding a putative tGCase from a cDNA library of the toad stomach, and found the predicted amino acid sequence to be distinct from that of tPCase. This putative tGCase was expressed in the stomach but not in other organs so far studied. It is of interest to note that its amino acid sequence showed higher homology with AMCase from the mouse stomach than with other known vertebrate chitinases of extra-stomach origin.
Chitinases are classified into 2 different families, namely, families 18 and 19, on the basis of the amino acid sequence similarity of their catalytic domain (Davies and Henrissat, 1995). Judging from the predicted amino acid sequence of the putative tGCase, this enzyme seems to belong to the family-18 chitinases. In these chitinases, the catalytic center of the chitinase activity was identified in a study using mutant recombinant chitinase (Renkema et al., 1998). In the case of family-18 chitinases, the second Asp (D) and Glu (E) in the DG-D-D-E motif of the N-terminal catalytic domain are considered to be essential for chitinase activity (Bleau et al., 1999). In addition, 6 cysteine residues forming 3 sets of disulfide bonds in the chitin-binding domain are reported to be essential for exerting chitinolysis (Tjoelker et al., 2000). In our putative tGCase, both of these structures were perfectly conserved (Fig. 3), suggesting that tGCase functions as a chitinolytic enzyme in the toad stomach."
Wersja tl'dr. Jest wiele rodzajów chitynazy, wykazano aktywność chitynazy podczas trawienia swoich chitynowych ofiar u płazów.
No ale przecież aksolotle, których dieta głównie składa się ze zwierząt które mają chitynowe pancerzyki, oczywiście na drodze ewolucji nie zyskały enzymów które potrafiłyby ją trawić.
Na całe szczęście są ludzie, bo co by aksolotle zrobiły, jakby nikt im nie obierał świerszczy i nie solił wody ...