Effect of nitrogen on activity of peptide hydrolases and protein content in caryopses and flag leaf of barley in ontogenesis

The aim of the research was to study the influence peculiarities of different levels of nitrogen nutrition on the activity of peptide hydrolases and protein content in ontogeny of barley plants.The paper discusses the content of total nitrogen, protein and the dynamics of activity of proteolytic enzymes during ontogenesis of barley plants. The activity of peptide hydrolases, the content of protein and total nitrogen were determined in four developmental phases in the flag leaf and forming caryopses of barley. The aim of the work was to determine the effect of different levels of nitrogen on the quantitative content of protein, the total amount of nitrogen, as well as on the activity of acidic and neutral peptide hydrolases. In the course of the research, the following features were revealed: 1. The content of total nitrogen and protein, as well as the activity of proteases, depended on the developmental phase and on the level of nitrogen nutrition; 2. Increasing doses of nitrogen contribute to a greater nitrogen outflow from flag leaves into the forming grain; 3. High nitrogen norms inhibit the activity of peptide hydrolases. 4. The highest rates of activity of acidic proteases were noted in the phase of full ripeness. 5. The total activity of peptide hydrolases increased in variants with a twoand three-fold nitrogen dose.

Some Aspects of Reparative Osteogenesis Optimization in Long Bone Fractures

The aim of the examination was to study the influence of some proteolytic enzymes (cathepcin-D, neutral proteinaze of serine group) upon formation of bone regenerate in fractures. There were 138 patients with bone fractures: 80 fractures were fresh, 38 - nonunited, 20 - nonconsolidated. Periosteal and transfragmental tissues were studied. Those materials were obtained during osteosynthesis that was performed at different terms after trauma. Results obtained allowed to make a suggestion that acid and neutral peptide-hydrolases influence the osteosynthesis and degradation of macromolecular components of bone organic matrix during reparative osteogenesis. That allowed detecting the new ways for optimization of reparative processes in fractures.

Aminopeptidase C of Aspergillus niger Is a Novel Phenylalanine Aminopeptidase

ABSTRACT A novel enzyme with a specific phenylalanine aminopeptidase activity (ApsC) from Aspergillus niger (CBS 120.49) has been characterized. The derived amino acid sequence is not similar to any previously characterized aminopeptidase sequence but does share similarity with some mammalian acyl-peptide hydrolase sequences. ApsC was found to be most active towards phenylalanine β-naphthylamide (F-βNA) and phenylalanine para-nitroanilide (F-pNA), but it also displayed activity towards other amino acids with aromatic side chains coupled to βNA; other amino acids with nonaromatic side chains coupled to either pNA or βNA were not hydrolyzed or were poorly hydrolyzed. ApsC was not able to hydrolyze N-acetylalanine-pNA, a substrate for acyl-peptide hydrolases.

Aspartic Peptide Hydrolases in Salmonella enterica Serovar Typhimurium

ABSTRACT Two well-characterized enzymes in Salmonella entericaserovar Typhimurium and Escherichia coli are able to hydrolyze N-terminal aspartyl (Asp) dipeptides: peptidase B, a broad-specificity aminopeptidase, and peptidase E, an Asp-specific dipeptidase. A serovar Typhimurium strain lacking both of these enzymes, however, can still utilize most N-terminal Asp dipeptides as sources of amino acids, and extracts of such a strain contain additional enzymatic activities able to hydrolyze Asp dipeptides. Here we report two such activities from extracts of pepB pepEmutant strains of serovar Typhimurium identified by their ability to hydrolyze Asp-Leu. Although each of these activities hydrolyzes Asp-Leu at a measurable rate, the preferred substrates for both are N-terminal isoAsp peptides. One of the activities is a previously characterized isoAsp dipeptidase from E. coli, the product of theiadA gene. The other is the product of the serovar Typhimurium homolog of E. coli ybiK, a gene of previously unknown function. This gene product is a member of the N-terminal nucleophile structural family of amidohydrolases. Like most other members of this family, the mature enzyme is generated from a precursor protein by proteolytic cleavage and the active enzyme is a heterotetramer. Based on its ability to hydrolyze an N-terminal isoAsp tripeptide as well as isoAsp dipeptides, the enzyme appears to be an isoAsp aminopeptidase, and we propose that the gene encoding it be designated iaaA (isoAsp aminopeptidase). A strain lacking both IadA and IaaA in addition to peptidase B and peptidase E has been constructed. This strain utilizes Asp-Leu as a leucine source, and extracts of this strain contain at least one additional, as-yet-uncharacterized, peptidase able to cleave Asp dipeptides.