Distribution of Chitinolytic Enzymes in the Organs and cDNA Cloning of Chitinase Isozymes from the Stomach of Two Species of Fish, Chub Mackerel (<i>Scomber japonicus</i>) and Silver Croaker (<i>Pennahia argentata</i>)

Abstract

Chitinolytic activities were measured in two fish species having different feeding habits, chub mackerel (Scomber japonicus) and silver croaker (Pennahia argentata). Chitinase (an endo-type chitinolytic enzyme) activity was measured using pNP-(GlcNAc)n (n = 2, 3) as substrates; its level was significantly high in the stomachs of both species, as well as in the gills, intestine, pyloric appendage, testis, and liver of chub mackerel and in the spleen, kidney, pyloric appendage, ovaries, heart, and liver of silver croaker. β-N-Acetylhexosaminidase (an exo-type chitinolytic enzyme) activity was measured using pNP-(GlcNAc) as a substrate; it was detected at high levels in many parts apart from the digestive tracts of both species. The optimum pH for chitinase activity was 3.0 -5.0 in the stomachs of both species, 4.0 in the liver of chub mackerel, and 4.0 and 8.0 in the kidney of silver croaker. Full-length cDNAs encoding two chitinase isozymes were obtained from the stomachs of the two fish species: SjChi-1 (1604 bp) and SjChi-2 (1512 bp) from chub mackerel and PaChi-1 (1630 bp) and PaChi-2 (1606 bp) from silver croaker. Expression analysis of these genes in the organs of the two species revealed strong expression of SjChi-1 in the stomach of chub mackerel and that of PaChi-1 and PaChi-2 in the stomach of silver croaker. The difference in the expression pattern of these genes is likely attributed to the difference in the feeding habits of the two fish species. Our results suggested the presence of novel chitinases in the two species.

Chondrichthyes Chitinase: Molecular Cloning, Distribution, and Phylogenetic Analysis

“…In contrast, DkChi was expressed in all organs of D. kwangtungensis, but chitinase activity was observed only in the stomach, and based on the feeding status of the three samples used in the current study, the possibility of adjustment for expression confined to the stomach exists. Conversely, Hex activity, which was measured using pNP-GlcNAc as the substrate, was detected in all organs, similar to previous reports [11] …”

“…Two varieties of the chitinase genes were obtained from the stomach of the fish and subjected to phylogenetic analysis, based on the deduced amino acid sequence 2 fish-specific groups, acidic fish chitinase-1 (AFCase-1) and acidic fish chitinase-2 (AFCase-2) were identified [6]. In addition, chitinase activity has been observed in organs, excluding the stomach, in the class of fish classified as Actinopterygii [11] [12], and a new group fish chitinase-3 (FCase-3), has been identified based on an isoform found in the stomach and kidneys [12]. In contrast, not even one chitinase gene of the AFCase-1, AFCase-2, and FCase-3 groups has been detected in the stomach of either Prionace glauca, classified as a Chondrichthyes, or the stomach of Latimeria chalmnae, classified as Sarcoptery-…”

Distribution of Chitinolytic Enzyme in the Organs and Molecular Cloning of a Novel Chitinase Gene from the Kidney of Marbled Rockfish <i>Sebastiscus marmoratus</i>

“…in digestive organs has been thought to play a role in the degradation of (GlcNAc) n into GlcNAc, produced via the effect of chitinases in the stomach [31]. It has been reported that fish contain chitinous substances in their scales [33], have chitin synthases [34], and have a mechanism of carbohydrate metabolism [35].…”

“…Furthermore, in fish, chitinase activity has been M. Watanabe et al DOI: 10.4236/abb.2018. 91004 38 Advances in Bioscience and Biotechnology observed not only in the digestive tract, but also in other organs [31]. Also, an acidic mammalian chitinase (AMCase) was found in mammals, which are vertebrates like fish, and this AMCase is involved in digestion and absorption of food [11].…”

Distribution of Chitinolytic Enzymes in the Organs and cDNA Cloning of Chitinase Isozymes from the Liver of Golden Cuttlefish <i>Sepia esculenta</i>

“…Chitinases in the fish stomach are classified into two groups based on differences in their primary structure and the patterns of degradation of (GlcNAc) n : acidic fish chitinase-1 (AFCase-1) and acidic fish chitinase-2 (AFCase-2) [16] [17] [18] [19]. Conversely, studies reporting the cDNA cloning and expression of chitinases and chitinase-like proteins from bivalves and gastropods, which are mollusks, have noted that these play roles in shell formation [20] [21] [22], immunity [23] [24] [25] [26], and digestion [27].…”