Human Gastric Juice Contains Chitinase That Can Degrade Chitin

Abstract

Chitin digestion by humans has generally been questioned or denied. Only recently chitinases have been found in several human tissues and their role has been associated with defense against parasite infections and to some allergic conditions. In this pilot study we tested the gastric juices of 25 Italian subjects on the artificial substrates 4-methylumbelliferyl-β-D-N,N’,diacetylchitobiose or/and fluorescein isothiocyanate (FITC) chitin to demonstrate the presence of a chitinase activity. Since this chitinase activity was demonstrated at acidic pH, it is currently referred to acidic mammalian chitinase (AMCase). AMCase activity was present in gastric juices of twenty of 25 Italian patients in a range of activity from 0.21 to 36.27 nmol/ml/h and from 8,881 to 1,254,782 fluorescence emission (CPS), according to the used methods. In the remaining five of 25 gastric juices, AMCase activity was almost absent in both assay methods. An allosamidine inhibition test and the measurement at different pH values confirmed that this activity was characteristic of AMCase. The absence of activity in 20% of the gastric juices may be a consequence of virtual absence of chitinous food in the Western diet.

Life cycle assessment of edible insects for food protein: a review

“…For example, for insect species where the exoskeleton is eaten, a low FCR is achieved; however, the exoskeleton is not digestible and does not provide nutritional value. However, it should be noted that chitinases (enzymes which breakdown chitin) have been found in the intestines of human populations with a higher rate of entomophagy (Paoletti et al 2007). …”

Why we still don't eat insects: Assessing entomophagy promotion through a diffusion of innovations framework

“…Insect-fortified flours can be marketed to those seeking higher protein-to-carbohydrate ratios in their diet, such as bodybuilders or followers of the Atkins diet [a cricket based power bar already exists (O'Callaghan, 2013)]. Chitin may also become a marketing tool (Goodman, 1989;Ramos-Elorduy, 1998): Previous authors assumed consumed insect chitin has no nutritional value to humans (Gorham, 1979), but the discovery that some humans do possess working chitinases (pointedly, those from low socioeconomic backgrounds who still depend on insects for protein) suggests that the role of chitin in human nutrition needs to be re-evaluated (Paoletti, Norberto, Damini, & Musumeci, 2007). Insects are also non-GMO and some species are gluten-free, although whether selling more insects is worth contributing to pseudoscientific or orthorexia-enabling dietary trends is debatable (Stein, 2014).…”

Microbiological aspects of processing and storage of edible insects

“…In general, the crude protein content of insects ranges from 40% to 75% on dry weight basis, largely depending on species and stage in the life cycle (Verkerk, Tramper, Van Trijp, & Martens, 2007). Although these values should be corrected (Ramos-Elorduy et al, 1997) for the N-containing chitin which represents approximately 5e20% of insect biomass, these are attractively high concentrations (Paoletti, Norberto, Damini, & Musumeci, 2007).…”