Enables glutamate-cysteine ligase activity and glutamate-cysteine ligase catalytic subunit binding activity. Involved in several processes, including cellular response to growth factor stimulus; cellular response to thyroxine stimulus; and response to gonadotropin. Part of glutamate-cysteine ligase complex. Human ortholog(s) of this gene implicated in myocardial infarction and vascular dementia. Orthologous to human GCLM (glutamate-cysteine ligase modifier subunit). [provided by Alliance of Genome Resources, Apr 2022]