Abstract: Two tissue electrodes are described in this paper. It is shown that a portion of intact tissue from apple or cactus can be coupled with potentiometric ammonia gas sensing electrode to prepare sensors for some amino acids with good response properties. Their optimum operating conditions and properties with respect to buffer sort, pHof the bulk solution, selectivity, linearity, stability, sensitivity and response time are studied and discussed. At the same time, the dynamic parameters, such as K_m and V_m, of L-glutamine deaminasc and L-as-paragine deamlnase have been obtained by means of these tissue electrodes.

Key words: Biosensors, Tissue electrodes, Biocatalysis, Apple, Cactus