Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: criteria for evaluation.

Protein quality, as determined by the PDCAAS method, is a measure of a protein's ability to provide adequate levels of essential amino acids for human needs. PDCAAS is calculated using an amino acid profile and true digestibility of a food protein. Soy protein is recognized as a high quality plant protein, but published PDCAAS values may vary based on the soy protein ingredient as well as the reproducibility and accuracy of the testing methods.

Effects of soy protein on lipoprotein lipids and fecal bile acid excretion in men and women with moderate hypercholesterolemia.

Background: Soy protein (SP) and low-fat dairy product consumption have been suggested to have hypocholesterolemic effects, although the responsible mechanisms are poorly understood.

Objective: This randomized, controlled, parallel arm trial evaluated the effects of an insoluble fraction of SP and total milk proteins (TMPs) with high calcium content on the fasting lipid profile. It also assessed the potential contributions of increased excretion of bile acids and neutral sterols to their lipid-altering effects.

Correlation of an immobilized digestive enzyme assay with poultry true amino acid digestibility for soybean meal.

The immobilized digestive enzyme assay (IDEA) was run on 6 soybean meal (SBM) samples and compared with true amino acid digestibility (TAAD) content, as determined using cecectomized roosters. The IDEA values were excellent TAAD predictors as evidenced by R(2) values of 0.90 and 0.

Fish meals, fish components, and fish protein hydrolysates as potential ingredients in pet foods.

An experiment to determine the chemical composition and protein quality of 13 fish substrates (pollock by-products, n = 5; fish protein hydrolysates, n = 5; and fish meals, n = 3) was conducted. Two of these substrates, salmon protein hydrolysate (SPH) and salmon meal with crushed bones (SMB), were used to determine their palatability as components of dog diets. Pollock by-products differed in concentrations of CP, crude fat, and total AA by 71, 79, and 71%, respectively, and GE by 4.

Chemical composition, protein quality, palatability, and digestibility of alternative protein sources for dogs.

The chemical composition and protein quality of 11 alternative protein sources (chicken products, blood products, enzyme-hydrolyzed fish protein concentrate, soybean meal, and spray-dried pork liver) were determined, and an experiment was conducted to determine palatability and digestibility of processed red blood cell-containing diets. Chicken protein sources differed in concentrations of CP, acid-hydrolyzed fat, and total AA (TAA) by 20, 31, and 24%, respectively, and GE by 1.7 kcal/g.

Inhibition of in vivo myocardial ischemic and reperfusion injury by a synthetic manganese-based superoxide dismutase mimetic.

We determined whether an organic superoxide dismutase mimetic could reduce myocardial injury resulting from a 90-min occlusion of the left circumflex coronary artery, followed by 18 hr of reperfusion in an anesthetized canine. The superoxide dismutase-mimetic studied (SC-52608) was a synthetic Mn-based macrocyclic compound. SC-52608 or the inactive analog SC-54385 was administered as four doses of 4 mg/kg i.

Protective effects of the SOD-mimetic SC-52608 against ischemia/reperfusion damage in the rabbit isolated heart.

An experimental model of myocardial ischemia/reperfusion injury was used to assess the cardioprotective effects of SC-52608, a low molecular weight superoxide dismutase mimetic. Langendorff perfused rabbit isolated hearts were subjected to 30 min of global ischemia followed by 45 min of reperfusion. Hearts perfused in the presence of 20 microM SC-52608 exhibited a decrease in the release of creatine kinase and intracellular potassium compared to hearts receiving vehicle (control).

A model of human small intestinal absorptive cells. 1. Transport barrier.

The Caco-2 cell culture model of human small intestinal absorptive cells was used to investigate transepithelial transport. Transport of permeability markers such as mannitol demonstrated that Caco-2 monolayers became less permeable with increasing age in culture. Cells were routinely used for transport studies between day 18 and day 32.

Synthetic peptide inhibitors of complement serine proteases--III. Significant increase in inhibitor potency provides further support for the functional equivalence hypothesis.

Synthetic peptides based on functionally equivalent (as defined by similar patterns of chemically equivalent amino acids) serine protease inhibitor (serpin) C-terminal sequences inhibit both classical and alternative pathways of complement activation. Inhibition was also found with hybrid peptides consisting of the cleavage site of one serpin (antithrombin III, alpha-1-antitrypsin, or antichymotrypsin) attached to the short and long functionally equivalent protease binding cores of the other two serpins. A hybrid peptide composed of the sequence at the site of cleavage of C4 by C1s attached to the long binding core of antithrombin III was selective in inhibiting the classical pathway with no effect on the alternative pathway at a concn of 10 microM.

Physiological and cytotoxic effects of Ca(2+) ionophores on Caco-2 paracellular permeability: relationship of 45Ca(2+) efflux to 51 Cr release.

The human intestinal cell line, Caco-2, and the Ca2+ ionophores, A23187 and ionomycin, were used to determine the interrelationships of 45Ca(2+) efflux, transepithelial electrical resistance (Rt), and [3H]-mannitol flux to changes in 51Cr release and lactate dehydrogenase (LDH) activity. Treatment of Caco-2 monolayers with ionomycin at concentrations of between 0.25 and 2.

Endocytosis and degradation of alpha 1-antitrypsin-protease complexes is mediated by the serpin-enzyme complex (SEC) receptor.

Alpha 1-Antitrypsin (alpha 1-AT) is similar to other members of the serine protease inhibitor (serpin) supergene family in that it undergoes structural rearrangement during the formation of a covalently stabilized inhibitory complex with its cognate enzyme, neutrophil elastase. We have recently demonstrated an abundant, high-affinity cell surface receptor on human hepatoma cells and human mononuclear phagocytes which recognizes a conformation-specific domain of the alpha 1-AT-elastase complex as well as of other serpin-enzyme complexes (Perlmutter, D. H.

Identification of a serpin-enzyme complex receptor on human hepatoma cells and human monocytes.

Formation of the covalently stabilized complex of alpha 1-antitrypsin (alpha 1-AT) with neutrophil elastase, the archetype of serine proteinase inhibitor serpin-enzyme complexes, is associated with structural rearrangement of the alpha 1-AT molecule and hydrolysis of a reactive-site peptide bond. An approximately 4-kDa carboxyl-terminal cleavage fragment is generated. alpha 1-AT-elastase complexes are biologically active, possessing chemotactic activity and mediating increases in expression of the alpha 1-AT gene in human monocytes and macrophages.

Identification of a second active site in laminin for promotion of cell adhesion and migration and inhibition of in vivo melanoma lung colonization.

Previously we reported that a pentapeptide (Tyr-Ile-Gly-Ser-Arg or YIGSR) from domain III of the B1 chain of laminin is a cell attachment site with the ability to stimulate cell adhesion and migration and to block experimental metastases. Here we report studies on the activities of synthetic peptides that cover domain III and report a second biologically active peptide PDSGR from this domain with activities similar to YIGSR. We also show that cyclic YIGSR is more potent in these assays than the linear peptide as expected since this sequence on laminin is bracketed by cysteines.

Synthetic peptide inhibitors of complement serine proteases--II. Effects on hemolytic activity and production of C3a and C4a.

Synthetic peptides based on the amino acid sequence at the site of cleavage of C3 by classical and alternative pathway convertases were found to be poor inhibitors of hemolysis except at concns of 1 mM and higher. Synthetic peptides of a second type, based on the C-terminal sequence of antithrombin III, were more effective; the best among them caused significant inhibition of hemolysis at a concn of 5 microM. A hybrid peptide composed of the sequence at the site of cleavage of C4 by C1s attached to an antithrombin III sequence was selective, inhibiting the classical pathway with no effect on the alternative pathway at a concentration of 25 microM.

Synthetic peptide inhibitors of complement serine proteases--I. Identification of functionally equivalent protease inhibitor sequences in serpins and inhibition of C1s and D.

Sequence homology comparisons between serum serine protease inhibitors led to the prediction that the C-terminal sequences are functionally equivalent and represent an essential protease binding domain. Inhibition of complement serine protease D cleavage of factor B and of C1s cleavage of C4 by synthetic peptides containing sequences from the C-termini of three serum serine protease inhibitors supports this prediction. These functionally equivalent peptides represent a new class of inhibitors of D and C1s as well as other serum serine proteases.

Interactions of S-(2-haloethyl)-mercapturic acid analogs with plasmid DNA.

A series of related S-(2-haloethyl)-L-cysteine analogs were synthesized and their interaction with DNA was studied with plasmid pBR322. Both S-(2-chloroethyl)-L-cysteine (CEC) and S-(2-bromoethyl)-L-cysteine (BrEC) rapidly induced relaxation of the supercoiled plasmid as determined by agarose gel electrophoresis and electron microscopy, whereas S-(2-fluoroethyl)-L-cysteine did not interact with DNA. The relaxation was most probably due to strand scission at alkylated labile sites in the DNA.

The hydrolysis and alkylation activities of S-(2-haloethyl)-L-cysteine analogs--evidence for extended half-life.

A series of S-(2-haloethyl)-L-cysteine derivatives, which are analogs of the proposed glutathione half-mustard metabolites of dihaloethanes, were synthesized and studied with respect to their hydrolysis and alkylation rates in aqueous solution. The trend of relative hydrolysis rates, Br greater than Cl much greater than F, paralleled their respective leaving group abilities; however, a dramatic rate increase was seen at pH 8 versus pH's 6 or 4. Hydrolysis of S-(2-chloroethyl)-L-cysteine analogs, where the ionizable groups were blocked (carboxyl esterified and/or N-acetylated), revealed that the amine moiety was responsible for the increased hydrolysis of mustard gas (beta, beta'-dichlorodiethyl sulfide) gave similar results with S-(2-chloroethyl)-L-cysteine, a finding which is consistent with the reaction intermediate being a highly charged species.

The binding mechanism of glutathione and the anti-tumor drug L-(alpha S, 5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125;NSC-163501) to gamma-glutamyltransferase.

The glutathione-protein binding interactions of rat renal gamma-glutamyltransferase (gamma GT) were studied by examining the effect of phenylglyoxal (PGO), a chemical modifying agent for arginyl residues. PGO inactivation of gamma GT followed pseudo-first order kinetics and the rate was dependent upon the concentration of PGO. Glutathione (GSH) protected the enzyme from inactivation by PGO.

Involvement of arginine residues in glutathione binding to yeast glyoxalase I.

Yeast glyoxalase I was inactivated by arginine-specific reagents. Inactivation by 2,3-butanedione, phenylglyoxal and camphorquinone 10-sulfonic acid followed pseudo first-order kinetics with the rate dependent upon modifier concentration. Extrapolation to complete inactivation showed modification of approx.

Phenol sulfotransferase. II. Inactivation by phenylglyoxal, N-ethylmaleimide and ribonucleotide 2',3'-dialdehydes.

Phenylglyoxal, a chemical modifying agent for arginine residues, produced rapid inactivation of a rat liver phenol sulfotransferase (3-phosphoadenylylsulfate:phenol sulfotransferase, EC 2.8.2.

Phenol sulfotransferase. I. Purification of a rat liver enzyme by affinity chromatography.

A phenol sulfotransferase (3-phosphoadenylylsulfate:phenol sulfotransferase, EC 2.8.2.