Search PubMed⌕ Search

Biomedical subjects

M Irie

Publications and source records attributed to M Irie.

At least 289 records · Page 16Linked to original sources
PubMed1981

Purification and properties of human urine ribonucleases.

1. Two RNases (RNase UL and RNase US) were purified from the urine of human adults by means of column chromatographies on SP-Sephadex C-50, phospho-cellulose and CM-cellulose and gel-filtration on Sephadex G-75 in homogeneous states obtained by SDS-disc electrophoresis. 2. Molecular weights of these RNases determined by gel-filtration were 38,000 and 13,000 for RNase UL and RNase US, respectively. 3. Optimal pH's of urine RNases were 8.0 and 6.75 for RNase UL and RNase US, respectively. 4. Chemical composition of urine RNases was determined. RNase UL contains about 20.7% of neutral sugar and 7.8% of hexosamine. RNase US contains a very small amount of carbohydrate moiety. 5. Base specificity of urine RNases studied with 2',3'-cyclic nucleotides and dinucleoside phosphates as substrates indicated that both RNases were pyrimidine specific and cytosine preferential enzyme, as is bovine pancreatic RNase A. Although base specificity of RNase UL was qualitatively similar to RNase A, that of RNase US was slightly different. That is, RNase US did not hydrolyze UpU and hydrolyzed UpC and 2',3'-cyclic UMP very slowly. 6. Antigenic properties of human urine RNases were studied by Ouchterlony's double diffusion analysis. RNase UL, RNase US, and RNase A were serologically distinguishable.

Adult↗
PubMed1980

Carboxamidomethylation of a ribonuclease from Aspergillus saitoi.

1) The inactivation of a RNase from Aspergillus saitoi (RNase Ms) was studied to obtain information on its active site. 2) Inactivation of RNase Ms by iodoacetamide was greater at an alkaline pH, and was protected more by 2',(3')-AMP than by 2',(3')-GMP. 3) Analysis of the hydrolysis products with 6 N HCl and alkaline treatment of carboxamidomethylated RNase Ms showed that the sites of reaction were one carboxyl group and one histidine residue. 4) Since the incorporation of a carboxamidomethyl group into carboxylic acid was not protected by 2',(3')-AMP, it was concluded that the formation of N1-carboxamidomethylhistidine was responsible for the loss of enzymatic activity of RNase Ms.

Adenosine Monophosphate↗
PubMed1980

Chemical modification of tryptophan residues in ribonuclease from a Rhizopus sp.

Tryptophan residues in ribonuclease from a Rhizopus sp. (RNase Rh) were modified by NBS, H2O2-dioxane, o-nitrophenylsulfenyl chloride (NPS-Cl) and the relation between the extent of modification and enzymatic activity was studied in each case. By extrapolation of the modified tryptophan residue-enzymatic activity curve to a completely inactive state, it was found that modification of 1-2 tryptophan residues is responsible for loss of enzymatic activity. RNase Rh was partly protected from modification by H2O2-dioxane (pH 8.4) and NPS-Cl (pH 3.5) when in the presence of 2'-AMP and the fluorescence emission spectrum of RNase Rh was quenched by adding 2'-AMP. It seems, therefore, that 1 or 2 tryptophan residues are involved in the active site of RNase Rh or are located near the active site. The solvent perturbation difference spectra of RNase Rh were measured using ethylene glycol and D2O as perturbants. The results indicated that 1.2 tryptophan residues for D2O and 1.9 tryptophan residues for ethylene glycol were exposed to the solvents. These data show that about 1.2-1.9 tryptophan residues are exposed to the solvent and their modification causes loss in enzymatic activity.

Amino Acids↗