Hydrolyses glutaminyl bonds, and activity is further restricted by preferences for the amino acids in P6 - P1' that vary with the species of potyvirus.
e.g. Glu-Xaa-Xaa-Tyr-Xaa-Gln \ (Ser or Gly) for the enzyme from tobacco etch virus.
^Fellers, J.P.; Collins, G.B.; Hunt, A.G. (1998). "The NIa-proteinase of different plant potyviruses provides specific resistance to viral infection". Crop Sci. 38: 1309–1319. doi:10.2135/cropsci1998.0011183x003800050030x.
^Kim, D.-H.; Choi, K.Y. (1998). "Potyvirus NIa protease". In Barrett, A.J.; Rawlings, N.D.; Woessner, J.F. (eds.). Handbook of Proteolytic Enzymes. London: Academic Press. pp. 721–723.
^Takahashi T, Nakanishi M, Yao Y, Uyeda I, Serizawa N (May 1998). "Direct formation of human interleukin-11 by cis-acting system of plant virus protease in Escherichia coli". Bioscience, Biotechnology, and Biochemistry. 62 (5): 953–8. doi:10.1271/bbb.62.953. PMID9648226.