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Biosynthesis and extrusion of β-chitin nanofibers by diatoms
Published in Antonio Trincone, Enzymatic Technologies for Marine Polysaccharides, 2019
Chitin biosynthesis and nanofiber self-assembly in the diatoms Cyclotella and Thalassiorsira are presumed to possess biochemical pathways and cellular processes consistent with those in other organisms that produce extracellular chitin (Merzendorfer 2011; Sugiyama et al. 1999). The core biosynthetic pathway for β-1,4-linked N-acetylglucosamine biopolymer formation consists of the following five main steps (shown in Figure 7.7): Fructose-6-P in the intracellular pool is converted to glucosamine-6-P via aminotransferase (EC 2.6.1.16) using l-glutamine, which is supplied from the GS/GOGAT pathway (see Figure 7.6).Glucosamine-6-P is converted to N-acetylglucosamine-6-P via N-acetyltransferase (EC 2.3.1.4) using acetyl co-A (coenzyme A) as the cosubstrate.The phosphate group on N-acetylglucosamine-6-P is changed from the 6-P to the 1-P position by phosphoacetylglucosamine mutase (EC 5.4.2.3).N-Acetylglucosamine-1-P is converted to uridine diphosphate (UDP)-N-acetylglucosamine via pyrophosphorylase (EC 2.7.7.23) using uridine triphosphate (UTP) as the cosubstrate.Chitin synthase (EC 2.4.1.16) catalyzes β-1,4-glycosidic bond formation between UDP-N-acetylglucosamine and (N-acetylglucosamine)n at the nonreducing end of the chain, releasing UDP and adding one monomer unit to the nonreducing end of the poly-N-acetylglucosamine chain.
Nuisance mucilage produced by Lindavia intermedia (Bacillariophyceae) in New Zealand lakes
Published in Inland Waters, 2022
Phil M. Novis, Tracey J. Bell, Putri Fraser, Cara A. Luiten, Simon F. R. Hinkley, Hugo Borges, Marc Schallenberg
New Zealand lake snow, which includes Lindavia cells and may contain other algae, bacteria, microinvertebrate fragments, and mineral material, is held together by microscopic threads. These threads seem to be principally composed of chitin (Novis et al. 2020), almost certainly β-chitin, which is known to be produced as spines or fibrils from marine-centric diatoms (Blackwell et al. 1967, Dweltz et al. 1968, Lindsay and Gooday 1985, Gügi et al. 2015). The chemical assay described here to measure chitin in lake snow revealed a strong relationship between the water column concentrations of material (dry weight) and the chitin concentrations (Fig. 2), and thus confirmed the earlier spectroscopic findings that chitin is a component of lake snow. Its correlation with summer chitin synthase expression (Fig. 3b) is additional evidence that the assay quantifies a product of interest.