Saccharomyces cerevisiae chitin biosynthesis activation by N-acetylchitooses depends on size and structure of chito-oligosaccharides

<p>Abstract</p> <p>Background</p> <p>To explore chitin synthesis initiation, the effect of addition of exogenous oligosaccharides on <it>in vitro </it>chitin synthesis was studied. Oligosaccharides of various natures and lengths were added to a chitin synthase assay performed on a <it>Saccharomyces cerevisiae </it>membrane fraction.</p> <p>Findings</p> <p><it>N</it>-acetylchito-tetra, -penta and -octaoses resulted in 11 to 25% [¹⁴C]-GlcNAc incorporation into [¹⁴C]-chitin, corresponding to an increase in the initial velocity. The activation appeared specific to <it>N</it>-acetylchitooses as it was not observed with oligosaccharides in other series, such as beta-(1,4), beta-(1,3) or alpha-(1,6) glucooligosaccharides.</p> <p>Conclusions</p> <p>The effect induced by the <it>N</it>-acetylchitooses was a saturable phenomenon and did not interfere with free GlcNAc and trypsin which are two known activators of yeast chitin synthase activity <it>in vitro</it>. The magnitude of the activation was dependent on both oligosaccharide concentration and oligosaccharide size.</p

The posthuman way of war

Recent interventions from a ‘posthumanist’ or ‘new materialist’ perspective have highlighted the embedded character of human systems within a ‘panarchy’ of human and non-human systems. This article brings attention to a very particular element of materiality, one with a profound significance for issues of security – relations between human and non-human animals in instances of conflict. It is an indication of the deeply human-centred character of both international relations and security studies that almost none of the central texts mention the very significant roles that non-human animals have in the conduct of war. We argue that the character of war would have been radically different but for the forced participation by an enormous range of non-human animals. Even though, with the improvements in transportation over the last century, non-human animals are less evident in the context of the movement of people and equipment, they still play a significant number of roles in the contemporary war-machines of wealthy countries. Drawing on literature from critical animal studies, sociology and memoirs, this article discusses the enormous variety of roles that non-human animals have played in the conduct of war, and examines the character of human–non-human animal relations in times of war