ELISA FOR DIFFERENTIAL QUANTITATION OF PLASMIN AND PLASMINOGEN IN CHEESE

Bovine plasmin (PLM) and its precursor plasminogen (PLG) are present i n cheese, in which the proteinase is thought to play a significant rol e in proteolysis during ripening. PLM in cheese is usually assayed by enzymic techniques and concentrations are generally expressed as activ ities. In order to determine absolute concentrations of PLM and PLG in cheese, me have applied an ELISA previously developed for the differe ntial determination of PLM and PLG in mill;. The assay used two monocl onal antibodies, one specific for PLG and the other cross reacting wit h PLM and PLG. PLM concentration ss;as obtained by subtracting the PLG concentration from the value for PLM plus PLG. The assay was evaluate d in cheese by determining the total amount of PLG and PLM in milk use d in the manufacture of eight semi-hard cheeses on a pilot plant scale , and comparing it with the total amount of PLG and PLM present in the eight corresponding wheys and unripened cheeses. Concentrations of PL G: and PLM in 19 commercial cheeses were also determined. It was thus demonstrated that the ELISA made it possible to quantify PLM and PLG i n milli and cheese and that PLM and PLG concentrations in cheese were highly dependent on the technology used for cheesemaking.