1. Isolation and some molecular properties of a trypsin-like enzyme from larvae of European corn borer Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae)
R Bernardi, G Tedeschi, S Ronchi, S Palmieri Insect Biochem Mol Biol. 1996 Sep-Oct;26(8-9):883-9. doi: 10.1016/s0965-1748(96)00057-4.
A one-step high-yielding procedure is presented for the purification of a trypsin-like proteinase from Ostrinia nubilalis larvae, consisting of benzamidine-sepharose affinity chromatography. The purified enzyme was homogeneous as judged by SDS-PAGE. The enzyme presents a molecular mass of 24 650 Da, a maximum pH activity profile of 9.5, a remarkable thermal stability and an optimum temperature of about 53 degrees C Km values determined using N alpha-benzoyl-DL-arginine-ethylester and N alpha-benzoyl-DL-arginine-p-nitro-anilide were 3.2 x 10(-5) M and 4.1 x 10(-4) M respectively. The proteinase was inhibited by some typical serine proteinase inhibitors such as N alpha-tosyl-L-lysine chloromethyl ketone, soybean trypsin inhibitors, benzamidine and phenylmethylsulfonyl fluoride. In particular, it was competitively inhibited by benzamidine with a Ki of 1.2 x 10(-5) M, whereas it was not affected by cysteine proteinases inhibitors. Comparative analysis of the amino acid composition and N-terminal sequence of O. nubilalis proteinase confirmed that this enzyme is very similar to other serine proteinases from lepidopteran larvae.
2. Studies on the catalytic action of poly-alpha-amino acids. VII. Stereospecificity in the enzyme-like hydrolysis of benzoyl-L-(D)-arginine-p-nitroanilides by copoly (Cys, Glu)
J Noguchi, N Nishi, S Tokura, U Murakami J Biochem. 1977 Jan;81(1):47-55. doi: 10.1093/oxfordjournals.jbchem.a131449.
The substrate specificity in the hydrolysis of L-, DL-, and D-BAPA (benzoylarginine-p-nitro-anilide) by copoly (L-Cys, L-Glu) and copoly (D-Cys, D-Glu) was studied, and enzyme-like stereospecific hydrolyses by poly-alpha-amino acids were identified for the first time. The L-type copolymer hydrolyzed L-BAPA faster than D-BAPA and the rates (v) of BAPA hydrolyses by L-type copolymer were found to be in the order vL greater than vDL greater than vD. On the other hand, the D-type copolymer hydrolysed D-BAPA faster than L-BAPA and the rates of BAPA hydrolyses by D-type copolymer were in the order vD greater than vDL greater than vL. In all cases, the reaction followed Michaelis-Menten kinetics when the substrate concentration was corrected, and the optimum conditions of the reaction were pH 6.0 and 40 degrees. The activity appeared after a certain amount of BAPA had combined with the polymer. D- and L-substrates combine competitively with the polymer and the different rates of hydrolysis are presumably due to the different substrate configurations in relation to the conformation of the active site in the polymer. The polymer shows activity near the range of random coil conformation, where some alpha-helical conformation is still present. Only some of the cysteine residues in the copolymer are involved in the hydrolytic activity.
