The supply of arginine may become rate limiting for enzymatic reactions that use this semiessential amino acid as a substrate (e.g., nitric oxide, agmatine, creatine, and urea synthesis), particularly under conditions of high demand such as growth, sepsis, or wound healing. In addition, arginine acts as a signaling molecule that regulates essential cellular functions such as protein synthesis, apoptosis, and growth. In the past decade, a number of carrier proteins for amino acids have been identified on the molecular level. They belong to different gene families, exhibit overlapping but distinctive substrate specificities, and can further be distinguished by their requirement for the cotransport or countertransport of inorganic ions. A number of these transporters function as exchangers rather than uniporters. Uptake of amino acids by these transporters therefore depends largely on the intracellular substrate composition. Hence, there is a complex crosstalk between transporters for cationic and neutral amino acids as well as for peptides. This article briefly reviews current knowledge regarding mammalian plasma membrane transporters that accept arginine as a substrate.

This study addresses the heterogeneity of family firms in their engagement with corporate social responsibility (CSR). We build on stewardship theory and socioemotional wealth to explore the foundations of CSR in family firms and to examine whether the extent of engagement is based on values, and how and why this happens. We use the interpretative method of grounded theory to address these questions. Based on 12 case studies of Spanish family firms, this article illustrates the patterns of influence of family involvement and values in explaining the extent and scope of CSR.

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