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I I Ivanova

Publications and source records attributed to I I Ivanova.

At least 19 recordsLinked to original sources
PubMed1992

A serine proteinase of an archaebacterium, Halobacterium mediterranei. A homologue of eubacterial subtilisins.

A homogeneous serine proteinase secreted by the extreme halophilic bacterium Halobacterium mediterranei 1538 was isolated by affinity chromatography on bacitracin-Sepharose with a yield of 48% (260-fold purification). The enzyme reveals an optimum for pyroglutamyl-Ala-Ala-Leu p-nitroanilide hydrolysis at pH 8.0-8.5 (Km 0.14 mM; k(cat). 36.9 s-1). Its activity increases linearly with NaCl concentration over the range 2-5 M. The substrate specificity of the enzyme is comparable with that of secretory subtilisins, the extent of protein degradation approaching that attained with proteinase K. The enzyme has a molecular mass of 41 kDa and a pI of 7.5. The N-terminal sequence of H. mediterranei serine proteinase reveals a 50% identity with that of Thermoactinomyces vulgaris serine proteinases, indicating that the enzyme belongs to the subtilisin family. Hence the serine proteinase secreted by the halophilic bacterium should be considered as a functional analogue, and a structural homologue, of eubacterial serine proteinases (subtilisins).

Amino Acid Sequence↗
PubMed1992

[Serine proteinase from the archaebacterium Halobacterium mediterranei--an analog of eubacterium subtilisin].

A homogeneous serine proteinase was isolated from cultural filtrates of the extreme halophilic bacteria Halobacterium mediterranei 1538 using affinity chromatography on bacitracin-Sepharose, ultrafiltration and gel filtration on Sephadex G-75, with a 48% yield and 260-fold purification. The enzyme was completely inactivated by specific inhibitors of serine proteinases, PMSF and DFP, as well as by Hg2+ and PCMB. The enzyme activity was strongly dependent of NaCl concentration, the enzyme being inactivated below 0.75 M NaCl. Inactivation of the enzyme was also seen in the presence of 2-7% organic solvents. The pH optimum for Glp-Ala-Ala-Leu-pNA hydrolysis is 8.0-8.5; Km is 0.14 mM, kcat is 36.9 s-1. The stability optimum lies at pH 5.5-8.0, temperature optimum is at 55 degrees C. The enzyme molecular weight is 41,000 Da; pI is 7.5. The substrate specificity of the enzyme is comparable to that of secretory subtilisins; the extent of protein substrate hydrolysis is similar to that of proteinase K. The N-terminal sequence of Halobacterium mediterranei serine proteinase, Asp-Thr-Ala-Asn-Asp-Pro-Lys-Tyr-Gly-Ser-Gln-Tyr-Ala-Pro-Gln-Lys-Val-Asn- Ala- Asp-, reveals a 50% homology with the aminoterminal sequence of Thermoactinomyces vulgaris serine proteinase. Hence, the serine proteinase secreted by halophilic bacteria may be considered as a structural and functional analog of eubacterial enzymes.

Amino Acid Sequence↗
PubMed1980

[Compensatory ovarian hypertrophy during alloxan diabetes and adrenoreceptor blockade].

The sexual cycle ceases in rats with alloxan diabetes. Chronic administration of phentolamine promoted interruption of the sexual cycle while obsidan was conducive to its preservation in part of the animals. Most diabetic rats both given and not given adrenoblockers showed the complete absence of compensatory hypertrophy of the ovary (CHO). As shown by the analysis, the content of gonadotropins in the pituitary glands of diabetic rats was increased, with the response to chorionic gonadotropin being close to normal. It is suggested that the absence of CHO in most diabetic rats can be accounted for by the fact that after removal of one ovary the hypothalamohypophyseal system does not secrete gonadotropins in adequate amounts.

Alloxan↗
PubMed1977

[Bistability in the activity of glutamine synthetase in ammonium-limiting chemostat cultures of Escherichia coli ML 30].

The approximative estimation of the function micron([NH+4]) in cultures of E. coli ML 30 had shown that bistability of the ammonium concentration in ammonium limited continuous cultures could be possible (BERGTER et al. 1977). This phenomenon suggested a bistability in the regulation of ammonia assimilation. Therefore, the activity of one key enzyme of the two ammonia assimilation systems was measured. The distribution of the activity of glutamine synthetase in ammonia limited continuous cultures after different transition states confirmed this suggestion.

Ammonia↗