Human serum contains a chitinase: identification of an enzyme, formerly described as 4-methylumbelliferyl-tetra-N-acetylchitotetraoside hydrolase (MU-TACT hydrolase)

Abstract

Since 1988 an endoglucosaminidase, provisionally named MU-TACT hydrolase, has been known that hydrolyses the artificial substrate 4-methylumbelliferyl-tetra-N-acetyl-chitotetraoside (MU-[GlcNAc]4, where GlcNAc is N-acetylglucosamine). The biological function of the enzyme was unknown. In this paper evidence is presented showing that this endoglucosaminidase from human serum is in fact a chitinase that is different from lysozyme. The facts sustaining this finding are: (i) the identification of the products formed from MU-[GlcNAc]3 and [GlcNAc]2;and [GlcNAc]3; (ii) chitin and ethylene glycolchitin can be degraded by the enzyme; (iii) the chitinase inhibitor allosamidin also inhibits the action of MU-TACT hydrolase from human serum; (iv) no hydrolysis of the lysozyme substrate Micrococcus lysodeikticus. The enzyme also occurs in rat liver. It was demonstrated that upon Percoll density gradient centrifugation the enzyme from this tissue distributed parallel to the lysosomal marker enzymes beta-N-acetylhexosaminidase and beta-galactosidase, indicating a lysosomal localization for this enzyme. It is proposed that the enzyme functions in the hydrolysis of chitin, to which mammals are frequently exposed during infection by pathogens.

Quantitative Changes in Serum Concentration of Bovine Gut Chitinase in Theileria Infection

“…There are some reports showing the existence of chitinase activities in the sera of the goat, guinea pig, and human [10,[12][13][14]. By use of the present immunoblotting, we also tested the possibility that the antibody against bovine gut chitinase could detect protein bands in the plasma of other animal species (Fig.…”

Discrimination between chitinase and chitobiase activities in Candida albicans.

“…The same effect of free GalNAc was observed for the Jack bean enzyme, although the degree of inhibition was higher (24%). It is improbable that step 1 of the above reaction pathway (removal of the outer G1cNAc) is catalyzed by the exo-enzyme a-N-acetylhexosaminidase, since in earlier work we already demonstrated that under the conditions employed here, /3-N-acetylhexosaminidase from Jack bean was virtually inactive towards this substrate (17). The above results suggested that the outer G1cNAc residue of MU-[G1cNAc]2 was removed by a chitobiase-like $-N-acetylglucosaminidase.…”

“…The mixtures were kept on ice for 15 min and were then centrifuged for 10 min at 12,000 X g. The supernatant (1,000,u1) was neutralized with 60,u1 of 2.0 M NaOH and desalted on small columns of Bio-Rad AG 50W-X8 (H+ form; bed-volume 500,u1), followed by Bio-Rad AG 1-X8 (acetate form; bed-volume 500,u1). The resulting preparations were analyzed by high-pressure liquid chromatography (HPLC) on a CarboPac PA-100 column (HPAEC-PAD), as we described before (17).…”

“…We recently described the existence of a chitinase present in human serum (17). To find out whether the latter enzyme could be discriminated from C. albicans chitinase in the case of infection with this microorganism, we conducted the present study.…”

Chitinolytic activity in viable spores of encephalitozoon species

“…Chitinase was found in vertebrates, in human, and in guinea pig serum (Overdijk & Van Steijn 1994, Overdijk et al 1996. Chitin is a component in the sheat of Brugia malayi (Fuhrman & Piessens 1985), Onchocerca volvu- …”