[Ribonuclease Fl1 from Fusarium lateriticum. Isolation, substrate specificity and amino acid sequence]. / Ribonukleaza Fl1 Fusarium lateriticum. Vydelenie, substratnaia spetsifichnost' i aminokislotnaia posledovatel'nost'.

Extracellular RNase Fl1 has been purified from the culture filtrate of Fusarium lateritium. The enzyme has been obtained in the electrophoretically homogeneous state with the yield about 90% and 300 fdd degree of purification. RNase Fl1 is a guanyl specific enzyme (EC 3.1.27.3) with the specific activity on RNA 1420 units/mg of protein. The total primary structure of the RNase has been determined by the automated Edman degradation of two non-fractionated peptide hydrolysates produced by trypsin and Staphylococcus aureus protease and of the hydroxylamine cleavage products of the protein. It was shown that hydroxylamine converts the RNase Fl1 N-terminal residue, pyroglutamic acid, into the hydroxyamic acid derivative sensitive to Edman degradation. RNase Fl1 consists of 105 amino acid residues (Mr 10,852) and is a structural homologue of the Fus. moniliforme RNase F1, differing from the latter by 15 amino acid substitutions outside the enzyme active site.

[Extracellular ribonuclease from Bacillus thuringiensis]. / Vnekletochnaia ribonukleaza iz Bacillus thuringiensis.

The ability of the strain Bacillus thuringiensis var. subtoxicus to produce extracellular ribonuclease (ribonuclease Bt) was studied. It was found that the culture medium possesses a RNA-depolymerizing activity whose maximum is observed 4-5 hours after the beginning of the linear growth phase. A three-step chromatography of the culture extract on phosphocellulose resulted in a homogeneous enzyme with a molecular mass of 12000 Da. The enzyme showed the maximum activity towards RNA at pH 8.5, catalyzed the hydrolysis of polyribonucleotides and guanosine-2',3'-cyclophosphate. Hence, the enzyme can be related to base-nonspecific cyclizing ribonucleases showing the guanylic specificity towards nucleoside-2',3'-cyclophosphates.