During phytopathological surveys conducted in the experimental fields of Research Institute of Viticulture and Winemaking leaf samples from different grapevine varieties with the phytoplasma symptoms have been collected. Phytoplasmas in diseased plants were detected by 16S-rDNA nested PCR method with the universal primers for phytoplasmas R16mF2 / R16mR1 and R16F2n/R16R2 and taxonomically characterized (Huseynova al., 2015). NAD-malate dehydrogenase (NAD-MDH) aspartate aminotransferase (AsAT) and alanine aminotransferase (AlAT) have been investigated in grapevine samples infected with "Candidatus Phytoplasma solani". Activities of all three metabolic enzymes increased in the leaves of infected plants compared with healthy plants. The increase of the enzymes activities caused by phytoplasma influence could be valued as plant response to infections.