Kurvjzieža kontemplācijas

[..] Until 1994 the human organism was not thought to produce chitinases, because of the absence of endogenous chitin in
human tissues, which means no need for enzymatic turnover and
remodeling of chitin structures. Therefore nutritionists have indicated chitin as a non-digestible polymer in the human organism
(Bukkens, 2005; DeFoliart, 1992) although chitin-containing foods
such as mushroom, crustaceans and insects are largely consumed,
especially in tropical countries. This assertion, however, has been
recenntly contradicted by reports describing up to nine mammalian
chitinases and chitinase-like genes that are present in man and
other mammals
[..]
Since the earliest discoveries, scientists hypothesized that mammalian chitinases take part in the innate immune response to
parasites, with the function of binding and digesting chitin structures such as cell walls, egg shells and cysts produced by many
organisms including fungi, protozoans and nematodes
Barone et al. (2003) detected higher chitotriosidase activity in
plasma of African children affected by acute malaria with respectto
reference values obtained in age-matched African children.
[..]
The state of the art of human activity of collecting, cultivating
and consuming chitin-bearing food such as crustaceans, insects and
mushrooms has been the object of several comprehensive ecological and ethnobiological investigations (DeFoliart, 1992; Paoletti &
Bukkens, 1997; Paoletti, 2005). The importance of entomophagy
has been also remarked by FAO, which stressed the great diversity and accessibility of this class of alimentary resources, being a
source of inorganics, proteins, vitamins and poly-unsaturated fatty
acids (Bukkens, 2005; Fontaneto et al., 2011).
More than 2000 species of arthropods are mostly used as food
by many populations worldwide, as extensively described and discussed by Posey (1984) for Amazonia, Ramos-Elorduy et al. (1997)
forCentralAmerica,Malaisse (1997)for centralAfrica, Zhi-Yi(2005)
for China, and Mitsihashi (2005) for Japan. For example, within the
Tukanoan population living in the Colombian Vaupes Amazon rain
forest, arthropods represent a fundamental source of food, providing 12–24% of total protein intake (Paoletti, Buscardo, & Dufour,
2000).
Chitin represents 5–20% of total dry-weight in adult crustaceans and insects. For this reason, Paoletti, Norberto, Damini, and
Musumeci (2007) and Paoletti, Norberto, Cozzarini, and Musumeci
(2009) suggested that a chitin-rich diet may influence chitinase
variability in human populations. Consequently they proposed that
the reduction of chitin intake in western diet may have reduced
selective pressure on the chitinase genes, probably resulting in the
loss of catalytic efficiency.
[..]
AMCase-dependent chitinolytic activity was finally proved in
humans and quantified by Paoletti et al. (2007) who analyzed
the gastric juice of 25 patients submitted to gastroscopy
[..]
Subsequent studies were performed to test in vitro the ability
of human gastric juices to hydrolyze natural chitin model obtained
from the wings of Calliphora vomitoria. Fly wings were found to
be only moderately digested by gastric juices even though AMCase
levels were high, thus no significant results were obtained from
these unpublished studies: it might be supposed however that in
the wings the chiral rigid chitin framework shown in Fig. 2 can
withstand the enzymatic attack better than other chitinous substrates.