摘要:

ABSTRACTAn extracellular α‐amylase fromBacillus amyloliquefaciens,isolated from dry onion powder, has been purified to homogeneity by ammonium sulfate fractionation, adsorption on starch, column chromatography on DEAE‐cellulose, and gel filtration on Sephadex G‐100 column. The enzyme consisted of one polypeptide chain with a molecular weight of 60,000. The isoelectric point was pH 5.2, the pH optimum 5.5 and the temperature optimum ranging from 50°‐70°C. Prolonged digestion by trypsin did not affect the catalytic properties of the enzyme. The Kmfor starch was 6.9 mg/ml. The enzyme was quite stable at 50°C, but lost about 85% of its activity at 60° after 30

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00631.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

ABSTRACTi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00632.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

ABSTRACTA model system for cytochrome P‐450 comprised of hemin, thiosalicylic acid, and solvent (acetone and water), oxidized cyclohemne and n‐hexane at pH 2.7. Oxidation of cyclohexane yielded more cyclohexanol than cyclohexanone under mild reaction conditions, whereas the oxidation of n‐hexane generated more 3‐ and 2‐hexanones than 3‐ and 2‐hemnols. Oxygen was a limiting factor in the reaction, and increased oxygen pressures increased the ratio of cyclohexanone to cyclohexanol formed. Lag time for product formation decreased in a linear fashion with an increase in temperature. In addition, cyclohexanone decreased relative to cyclohexanol as the temperature was increased. Antioxidants increased the lag time for product formation, but had little effect on the final quantity or ratios of the oxidative products generated. 1,3 Diphenylisobenzafiran had no effect on the lag time, whereas Tiron and catechol increased the lag time. In contrast to aliphatic thiols, aromatic thiols were capable of driving the oxidative reaction. The model hemin system was approximately 6% as active as natural cytochrome P‐450. Hemin immobilized on glass beads effectively catalyzed the oxidation

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00633.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

ABSTRACTi

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00634.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

ABSTRACTEndothia parasiticaprotease shows hysteretic behavior (a lag phase) when acting upon L‐leucyl‐L‐leucine amide at pH 4.5. Initially, the products are L‐leucyl‐L‐leucine, L‐leucyl‐L‐leucyl‐L‐leucine and L‐leucine amide with little formation of L‐leucine and no ammonia. The relative concentration of L‐leucyl‐L‐leucine is about one‐fourth that of L‐leucine amide. As the reaction continues the relative concentration of L‐leucine increases slowly until it is equal to the concentration of L‐leucyl‐L‐leucine near the end of the reaction with each being one‐fourth that of L‐leucine amide. Formation of these products can only be explained by a combination of transpeptidation and hydrolytic reactions. By itself, L‐leucyl‐L‐leucine is cleaved very slowly but when mixed with L‐leucyl‐L‐leucine amide the rate is several fold greater than the combined rates of the two alone. L‐Leucyl‐L‐leucyl‐L‐leucine and L‐leucyl‐L‐leucyl‐L‐leucine amide as substrates ofE. parasiticaprotease give normal kinetic behavior with no evidence of formation of higher molecular weight compounds. Addition of as little as 1 μM L‐leucyl‐L‐leucyl‐L‐leucine (Km= 0.348 mM) to a reaction containing 1 mM L‐leucyl‐L‐leucine amide increases the rate of reaction with a shortening of the lag phase. Addition of 100 μM L‐leucyl‐L‐leucyl‐L‐leucine to such a reaction eliminates the hysteretic behavior. It is proposed thatE. parasiticaprotease is initially in an inactive form which can be activated by substrates as small as L‐leucyl‐L‐leucyl‐L‐leucine but not by L‐leucyl‐L‐leucine amide. During the lag phase observed with substrates such as L‐leucyl‐L‐leucine amide, the enzyme produces, via acyl transpeptidation, larger compounds which can rapidly activate the enzyme. While in the activated form,E. parasiticaprotease cleaves L‐leucyl‐L‐leucine amide via normal kinetic behavior; however, both acyl transpeptidation and hydrolysis still occur as shown by the relative concentrations of L‐leucine, L‐leucyl‐L‐leucine and L‐leucine amide of 1:1:4 near end of the reaction.E. parasiticaprotease cannot

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00635.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Book Reviews in this article.How to Write and Publish a Scientific Paper.Physicochemical Aspects of Protein Denaturation.Gas Chromatography with Glass Capillary Columns.Electron Microscopy of EnzymesThe Yeasts, Vol. 2. Physiology and Biochemistry of Yeasts.

ISSN:0145-8884    

DOI:10.1111/j.1745-4514.1979.tb00636.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY