Naotomo Tominaga

Isolation and characterization of a proteinase from white gourd

Abstract A proteinase from the sarcocarp of Benincasa cerifera was purified. ItsMW was estimated by two different methods to be about 50000. The maximum activity was found in the alkaline pH region against casein as a substrate. The enzyme was strongly inhibited by di-isopropyl fluorophosphate and not inhibited by EDTA and p -chloromercuribenzoic acid.

Isolation and characterization of a protease from Phytolacca americana

Abstract A cysteine protease of M r 26 000 has been isolated in homogeneous form from the fruit juice of Phytolacca americana . The enzyme, named phytolacin, has a maximum activity in the pH range 7.5–9.0 and contains carbohydrate moiety. The substrate specificity of phytolacin differs from that of papain.

Soybean trypsin inhibitor-C: An active derivative of soybean trypsin inhibitor composed of two noncovalently bonded peptide fragments.

Soybean Kunitz trypsin inhibitor (STI) has been shown to contain 197 amino acid residues (M.W. 21,500) and to have two disulfide bonds and two methionine residues (104 and 135), (fig. l), [l] . Since one methionine residue (135) is located in the position between the two disulfide-bond loops, cyanogen bromide treatment [2] of the native ST1 yields two peptide fragments. The present communication describes experiments on the cleavage of native ST1 by cyanogen bromide treatment to yield two fragments: STI-L (residues 1 to 135) and STI-S (residues 136 to 197). None of the fragments showed the trypsin-inhibitory activity. However, the two fragments can associate to form an active, noncovalently bonded, derivative designated STI-C (STI-CNBr) which possesses more than 80% of the native trypsin-inhibitory activity.

Properties of a New Plant Serine Protease Cucumisin

Cucumisin [EC 3.4.21.25] was coupled to cyanogen bromide-activated Sephayose 4B. The specific activity of the immobilized cucumisin was 41% of that of the soluble cucumisin toward casein. The immobilized enzyme was more stable against alkaline inactivation or heat than the soluble enzyme. In using affinity chromatography on a column of the immobilized cucumisin-Sepharose, cucumisin inhibitor was not obtained from potent sources of proteinase inhibitors, such as pig kidney and liver, avian and turtle egg-whites, or soybeans.

Active site titration of the serine protease cucumisin from Cucumis melo

Abstract The amount of active enzyme in cucumisin solution was determined by titration with N-acetyl- l -alanyl- l -alanyl-α-azaalanine p-nitrophenyl ester. When azapeptide was added to cucumisin, p-nitrophenol was rapidly released and deacylation was slow. The cucumisin used was found to be approximately 94% active.

Photochemical oxidation of snake gourd proteinase A2, a serine proteinase

Abstract Snake gourd proteinase A 2 was rapidly inactivated by methylene blue catalysed photooxidation at pH 7.8 and 25°. The rate of inactivation was pH-dependent and became slower at lower pH values, suggesting the involvement of some histidine residues in the inactivation. Changes in amino acid composition occurred only with histidine residues. One mole or more of histidine residues in the molecule are of essential importance in the catalytic function of snake gourd proteinase A 2 .