The Penzyme Milk Test

The enzyme exploited in the Penzyme milk test (Neogen Corporation, Michigan, USA) for P-lactam residues is D,D-carboxypeptidase. The assay is based on the following two properties of d, D-carboxypeptidase  

It is specifically and quantitatively inhibited by f)-lactam antibiotics thus, the more the sample is contaminated with these antibiotics, the further the residual enzyme activity will be reduced. 

It specifically hydrolyzes substrates of the R-o-Ala-D-Ala type with the liberation of D-alanine. 

In general, the Penzyme test is applicable for screening milk samples for the presence of f)-lactam compounds with detection limits close to the USFDA tolerances (Table 5.6) and is, therefore, applicable for the regulatory monitoring in accordance with the USA system. However, in all cases the detection limits quoted are greater than the current EU MRLs, and for that reason the test is not considered as a useful monitoring tool for the European market. 

TABLE 5.5 Range of Charm II Test Kits and Their Applications Currently Available for Antibiotic Residue Screening from Charm Sciences Inc. 

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TABLE 5.6 Manufacturer s Reported Detection Limits for the Penzyme Milk Test and the Delvo-X-PRESS for Various fS-Lactam Compounds in Spiked Bovine Milk Compared to USEDA Tolerances and EU MRLs... 

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