Arginase from kiwifruit: properties and seasonal variation

The in vitro activity of arginase (EC 3.5.3.1) was investigated in youngest-mature leaves and roots (1-3 mm diameter) of kiwifruit vines (Actinidia deliciosa var. deliciosa) during an annual growth cycle, and enzyme from root material partially purified. No seasonal trend in the specific activity of arginase was observed in roots. Measurements in leaves, however, rose gradually during early growth and plateaued c. 17 weeks after budbreak. Changes in arginase activity were not correlated with changes in the concentration of arginine (substrate) or glutamine (likely end-product of arginine catabolism) in either tissue during the growth cycle. Purification was by (NH4)2SO4 precipitation and DEAE-cellulose chromatography. The kinetic properties of the enzyme, purified 60-fold over that in crude extracts, indicated a pH optimum of 8.8, and a Km (L-arginine) of 7.85 mM. Partially-purified enzyme was deactivated by dialysis against EDTA, and reactivated in the presence of Mn²⁺, Co²⁺, and Ni²⁺

Nonlinear Supersymmetry as a Hidden Symmetry

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Plagiarizing plants: amino sugars as a class of glycosidase inhibitors.

Many polyhydroxylated alkaloids from plants are specific inhibitors of glycosidases. Information about these has led to the development of a wide range of both naturally occurring and synthetic inhibitors which may be used for mechanistic studies and for the purification of these enzymes. Sugar lactones are starting materials for highly efficient syntheses of deoxymannojirimycin and deoxyfuconojirimycin and of a number of their iminoheptitol analogues. This has allowed an investigation of the relationship between mannosidase and fucosidase inhibition

Inhibition of mammalian digestive disaccharidases by polyhydroxy alkaloids.

Several polyhydroxy alkaloids, including the eight presently known to occur in plants, have been compared as inhibitors of mouse gut digestive disaccharidases. The indolizidine castanospermine inhibited all activities tested, but others showed a selectivity which could be of value in studies of carbohydrate digestion and errors of metabolism

Synthesis of the enantiomers of 6-epicastanospermine and 1,6-diepicastanospermine from D- and L-gulonolactone.

The synthesis of the enantiomers of 6-epicastanospermine and of 1,6-diepicastanospermine from the enantiomeric gulonolactones is reported and the structure of the former is established as (1S,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydroindolizine. The inhibitory activities of the diastereomers against the amyloglucosidase-catalysed hydrolysis of p-nitrophenyl alpha-D-glucopyranoside were investigated, and the effects of 6-epicastanospermine and of 1,6-diepicastanospermine on 14 human liver glycosidases are reported

Language use before and after Stonewall: a corpus-based study of gay men’s pre-Stonewall narratives

This study presents a contrastive corpus linguistic analysis of language use before and after Stonewall. It uses theoretical insights on normativity from the field of language and sexuality to investigate how the shifting normativities associated with the Stonewall Riots (1969) – widely considered the central event of gay liberation in the Western world – have shaped our conceptualization of sexuality as it surfaces in language use. Drawing on two corpora of gay men’s pre-Stonewall narratives dating from two time periods (before and after Stonewall, called PRE and POST), the analysis combines quantitative (keyword analysis, collocation analysis) and qualitative (concordance analysis) corpus linguistic methods to examine discursive shifts as evident from narrators’ language use. The study identifies the terms homosexual and normal as central contrastive labels in PRE, and gay and straight as corresponding terms in POST. Other discursive shifts detected are from sexual desire/practices to identity (and vice versa), from an individualistic to a community-based conceptualization of sexuality, and from unquestioned heteronormativity and gender binarism to a weakening of such dominant discourses. The findings are discussed in relation to the desire-identity shift, which is traditionally assumed to have taken place at the end of the 19th century, and shed new light on Stonewall as a central event for the development of an identity-based conceptualization of sexuality as we know it today