Amino acid metabolism and the energetics of growth

The nonessential amino acids are involved in a large number of functions that are not directly associated with protein synthesis. Recent studies using a combination of transorgan balance and stable isotopic tracers have demonstrated that a substantial portion of the extra‐splanchnic flux of glutamate, glutamine, glycine and cysteine derives from tissue synthesis. A key amino acid in this respect is glutamic acid. Little glutamic acid of dietary origin escapes metabolism in the small intestinal mucosa. Furthermore, because glutamic acid is the only amino acid that can be synthesized by mammals by reductive amination of a ketoacid, it is the ultimate nitrogen donor for the synthesis of other nonessential amino acids. Because the synthesis of glutamic acid and its product glutamine involve the expenditure of adenosine triphosphate (ATP), it seems possible that nonessential amino acid synthesis might have a significant bearing on the energetics of protein synthesis and, hence, of protein deposition. This paper discusses the topic of the energy cost of protein deposition, considers the metabolic physiology of amino acid oxidation and nonessential amino acid synthesis, and attempts to combine the information to speculate on the overall impact of amino acid metabolism on the energy exchanges of animals.     

Physico-chemical and immunological properties of allophycocyanins

Allophycocyanins were purified from diverse cyanobacteria and one rhodophytan alga (Cyanidium caldarium). The native proteins are trimeric molecules with the structure ()₃. Representative native allophycocyanins and their and subunits were characterized with respect to molecular weight, amino acid composition, isoelectric point, absorption and fluorescence spectra and immunological properties. All of the allophycocyanins studied were strikingly similar with respect to each of these properties.Renatured and subunits of allophycocyanin were distinct immunologically from each other, and both cross-reacted with the antiserum to the native protein.Trimeric allophycocyanin was readily reconstituted from the purified and subunits. Formation of hybrid allophycocyanins was demonstrated by direct isolation and characterization of the hybrid proteins and by immunological techniques.The results support the view that allophycocyanins are a highly conserved group of proteins.Abbreviation Used SDS sodium dodecyl sulfate     

The energetics of organic synthesis inside and outside the cell

Thermodynamic modelling of organic synthesis has largely been focused on deep-sea hydrothermal systems. When seawater mixes with hydrothermal fluids, redox gradients are established that serve as potential energy sources for the formation of organic compounds and biomolecules from inorganic starting materials. This energetic drive, which varies substantially depending on the type of host rock, is present and available both for abiotic (outside the cell) and biotic (inside the cell) processes. Here, we review and interpret a library of theoretical studies that target organic synthesis energetics. The biogeochemical scenarios evaluated include those in present-day hydrothermal systems and in putative early Earth environments. It is consistently and repeatedly shown in these studies that the formation of relatively simple organic compounds and biomolecules can be energy-yielding (exergonic) at conditions that occur in hydrothermal systems. Expanding on our ability to calculate biomass synthesis energetics, we also present here a new approach for estimating the energetics of polymerization reactions, specifically those associated with polypeptide formation from the requisite amino acids.     

Physico-chemical and antigenic properties of adenovirus filaments

Hydrophobic interactions are shown to be predominant in stabilization of the quaternary structure of the adenovirus fiber and in preservation of its antigenic activity. The computer analysis has revealed at least five peptides with maximal hydrophilicity in the fiber protein composition. They may participate in the formation of antigenic determinants. The presence of type-specific, subgenus-specific, intersubgenus-specific and new genus-specific (common for both human and monkey Ad) antigenic determinants are determined in the composition of the Ad h1 fiber by the enzyme-immunoassay.     

Physico-chemical properties of lysyl-tRNA-synthetase from the rat liver

Two lysyl-tRNA-synthetase forms are obtained from the rat liver. Their molecular masses are determined by electrophoresis and gel-filtration on Sephadex G-150: form I-122, form II-64 kDalton. Gel-electrophoresis in the presence of 0.1% SDS indicates that form I of lysyl-tRNA-synthetase consists of two subunits with a molecular mass of 64 kDalton each, i. e. it is a dimer. Optimal conditions and kinetic parameters (Km and Vmax) of aminoacylation for the both enzyme forms are similar. Amino acid composition, fluorescence parameters and thermal inactivation conditions are determined.     

微生物代谢环境难降解性有机物的酶学研究进展

随着人类社会的快速发展,工业化水平不断提高,产生大量的污染物并排放到环境中,给人类的生活和身体健康造成了严重的影响。这些污染物中包含种类繁多的难降解有机物,如多芳香烃(PAHs)、环硝胺类物质(RDX、HMX和CL-20)、多氯联苯(PCBs)及烷烃类化合物等,对自然界的污染危害大。微生物可以消除它们对污染的影响,研究结果表明微生物的代谢或共代谢活动是降解这些物质的有效途径,降解起始阶段需要一些关键酶的参与活动,以氧化还原酶为主。这些氧化还原酶一般与细胞膜上其他的活性组分在一起,形成一个氧化还原系统氧化底物。被氧化的中间物质再通过一系列酶催化继续氧化成三羧酸中间代谢产物被微生物所利用。以下综述了与这些物质降解相关的代谢途径和关键的酶,展望今后在开展这类研究工作时要加强降解微生物的筛选和相关酶学的研究,进一步研究这些污染物的代谢或共代谢途径和机理,为工程化治理环境污染提供依据。     

Rice lectin: Physico-chemical and carbohydrate-binding properties

Rice seeds contain a 2-acetamido-2-deoxy- -glucose-specific lectin. It has an M_r of 36 000 and is composed of two identical, non-covalently bound subunits of M_r 18 000. Each subunit consists of two disulfide-linked polypeptide chains of M_rs 10 000 and 8000. The lectin activity is highly stable to several chemical denaturants and heat treatment. The lectin interacts with glycoproteins, which have either clustered O-linked oligosaccharides or N-linked oligosaccharides. The N-linked glycoproteins include high -mannose, hybrid and complex biantennary structures.     

Physico-chemical properties of rat and dog cardiac alpha-actinin

alpha-Actinin exists in several polymorphic forms which appear to be characteristic of the muscle type from which it is isolated. In order to determine the possible physiological role of this structural protein in cardiac muscle, we describe and compare here the physico-chemical properties of cardiac alpha-actinin from two different mammalian species, rat (fast contracting muscle) and dog (slow contracting muscle). Purification of cardiac alpha-actinin was achieved by chromatography on DEAE-cellulose and hydroxyapatite columns. The alpha-actinins isolated were different in their electrophoretic mobility (SDS-polyacrylamide gel electrophoresis), molecular size and alpha-helical content. However, their shape as revealed by electron microscopy and their activating effect on Mg2+-ATPase activity of actomyosin appear to be similar. These studies suggest that the rat and dog cardiac alpha-actinin are structurally different but functionally similar proteins.     

Physico-chemical and thermodynamic properties of monomeric Concanavalin a

An alkylated monomer of Concanavalin A was prepared photochemically according to the method of Tanaka et al. (1981). Its affinities for methyl--d-gluco, methyl--d-manno and p-nitro-phenyl--d-manno pryranoside were calculated. The enthalpies of these binding reactions were measured calorimetrically and the thermodynamic parameters were calculated. The values obatined suggest that the structure of the monomer differs from that of the dimeric and tetrameric molecules.Calorimetric studies also showed that the monomeric derivative reacts with IgM but not IgG. The enthalpy per binding site in the monomer-IgM reaction is equal to that of the monomer-mannose derivative reaction; mannose is the terminal residue of the saccharide chains of the IgM molecule. The stoichiometry of the reaction is ten ConA-m per IgM molecule.     

Physico-chemical properties of microbial antigens and the immuno-allergic tests]

Experiments were conducted on guinea pigs sensitized by the delayed and immediate types of allergy. Different antigens obtained from the strain of Brucella abortus BA-19 were used for sensitization and the resolving action. Comparison of the resolving properties of the corpuscular, soluble (ultrasound treated) antigens and purified protein fractions, polysaccharide and RNA was carried out in the skin reactions of the immediate and delayed type, passive skin anaphylaxis, acute anaphylactic shock, and the Schults-Dale test. Immediate reactions to the purified protein fraction were weaker than those to the whole soluble antigen, by which the animals were sensitized. Polysaccharide and the RNA-fractions proved to be inactive in the allergic reactions.     

Physico-chemical properties and heterogeneity of Alcaligenes faecalis polysaccharide

Two species of O-antigenic molecules with following sedimentation characteristics S(o)20, W 1,25.10(-13) S, D(o)20, W 9,7.10(-7) cm2/s, M 8000 and S(o)20, W 2,5.10(-13) S, D(o)20, W 5.10(-7) cm2/s, M 23,000-30,000 were detected in the cell wall of the strain Alcaligenes faecalis, a representative species of conditionally pathogenic microorganisms with unidentified taxonomic position. "Light" and "heavy" types of molecules have a lipopolysaccharide nature and show no differences in the monosaccharide composition of the polysaccharide moiety, structural organization of O-chain, or lipid A fatty-acid composition.