ARHGEF12 and infection: Indeed, intestinal microbiota and the hypoxic microenvironment of the gut trigger a constitutive expression of L-arg converting enzymes such as Arg1 in intestinal tissues.52,79 Importantly, during inflammation or infection the expression and/or function of multiple L-arg converting and/or depriving enzymes can be enhanced emptying L-arg supplies and turning L-arg into a nutritionally essential amino acid.