The amount of a N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase when measured in blood serum. The trait is level of N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase in blood serum (OBA_2040532, an Ontology of Biological Attributes entry). Also known as: blood serum N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase amount.