Adaptive Changes of Some Enzyme Activities in Rats and Humans to Dietary Protein

A study of the adaptive changes of some enzyme activities to the dietary protein intake was made in the liver, kidney, and pancreas of rats and serum of humans. The rats fed the 40 per cent casein diet had a higher rate of weight gain and the weights of the liver and kidney were higher than in the rats fed the 10 per cent casein diet. Three enzymes involved in the elimination of excess nitrogen from the body were found to show a similar response to increased dietary protein intake. These enzymes were: D-amino acid oxidase in the kidneys, arginase in the liver and kidneys, and glutamic-pyruvic transaminase in the liver of rats. The rate of enzyme induction was detectable the second day, being high during the first four days and reaching the maximum value on the fourth day. Thereafter, the enzymatic activity did not change much. The alkaline phosphatase activities in the liver and kidneys of the rats did not show significant change during consumption of the diets containing 10 per cent or 40 per cent casein. Samples of pancreatic trypsinogen and chymotrypsinogen of the rats were not collected during the appropriate time to note any significant changes caused by the diets . A more appropriate experimental design, including proper timing for feedings and dissections, for the study of the adaptation of the proteolytic enzymes in the pancreas of the rats is desirable and recommended. The values for the circulating enzymes of the human serum, 0-amino acid oxidase, glutamic-pyruvic transaminase, and alkaline phosphatase were not found to be affected significantly by the diets containing 12 per cent and 30 per cent protein calories

Experimental Evidence for a Metallohydrolase Mechanism in Which the Nucleophile Is Not Delivered by a Metal Ion: EPR Spectrokinetic and Structural Studies of Aminopeptidase from \u3cem\u3eVibrio proteolyticus\u3c/em\u3e

Metallohydrolases catalyse some of the most important reactions in biology and are targets for numerous chemotherapeutic agents designed to combat bacterial infectivity, antibiotic resistance, HIV infectivity, tumour growth, angiogenesis and immune disorders. Rational design of inhibitors of these enzymes with chemotherapeutic potential relies on detailed knowledge of the catalytic mechanism. The roles of the catalytic transition ions in these enzymes have long been assumed to include the activation and delivery of a nucleophilic hydroxy moiety. In the present study, catalytic intermediates in the hydrolysis of L-leucyl-L-leucyl-L-leucine by Vibrio proteolyticus aminopeptidase were characterized in spectrokinetic and structural studies. Rapid-freeze-quench EPR studies of reaction products of L-leucyl-L-leucyl-L-leucine and Co(II)-substituted aminopeptidase, and comparison of the EPR data with those from structurally characterized complexes of aminopeptidase with inhibitors, indicated the formation of a catalytically competent post-Michaelis pre-transition state intermediate with a structure analogous to that of the inhibited complex with bestatin. The X-ray crystal structure of an aminopeptidase–L-leucyl-L-leucyl-L-leucine complex was also analogous to that of the bestatin complex. In these structures, no water/hydroxy group was observed bound to the essential metal ion. However, a water/hydroxy group was clearly identified that was bound to the metal-ligating oxygen atom of Glu152. This water/hydroxy group is proposed as a candidate for the active nucleophile in a novel metallohydrolase mechanism that shares features of the catalytic mechanisms of aspartic proteases and of B2 metallo-b-lactamases. Preliminary studies on site-directed variants are consistent with the proposal. Other features of the structure suggest roles for the dinuclear centre in geometrically and electrophilically activating the substrate

Conformational States of Cytochrome P450 Oxidoreductase Evaluated by Förster Resonance Energy Transfer Using Ultrafast Transient Absorption Spectroscopy

NADPH-cytochrome P450 oxidoreductase (CYPOR) was shown to undergo large conformational rearrangements in its functional cycle. Using a new Förster resonance energy transfer (FRET) approach based on femtosecond transient absorption spectroscopy (TA), we determined the donor–acceptor distance distribution in the reduced and oxidized states of CYPOR. The unmatched time resolution of TA allowed the quantitative assessment of the donor–acceptor FRET, indicating that CYPOR assumes a closed conformation in both reduced and oxidized states in the absence of the redox partner. The described ultrafast TA measurements of FRET with readily available red–infrared fluorescent labels open new opportunities for structural studies in chromophore-rich proteins and their complexes

CONTRIBUTION OF THE KNEE JOINT TO MECHANICAL ENERGY IN CROUCHING START ACCORDING TO THE BACKWARD BLOCK INCLINED ANGLE INCREASE

The purpose of this study was to analyze the contribution of the knee joint to mechanical energy in crouching start according to the backward block inclined angle increase(F, F1, F2). Using kinetic and kinematic data from 3 university sprinters participating in this study we calculated the energies absorbed and generated by the knee joints. The analysis is limited to a two-dimensional (sagittal plane) exercise. Comparing mean values of the energy absorbed and generated from lower extremity joints of each subjects according to backward block inclined angle increase (F, F1, F2). We generate a ratio of a total energy absorbed and generated from lower extremities to one from knee joints. The generated energy of knee joints during start was the highest for all subjects and the absorbed energy of those was the lowest at 55 degree of backward block angle, or F, for subject 1, 50 degree for subject 2, and 50 degree for subject 3

Chondrosarcoma: With Updates on Molecular Genetics

Chondrosarcoma (CHS) is a malignant cartilage-forming tumor and usually occurs within the medullary canal of long bones and pelvic bones. Based on the morphologic feature alone, a correct diangosis of CHS may be difficult, Therefore, correlation of radiological and clinicopathological features is mandatory in the diagnosis of CHS. The prognosis of CHS is closely related to histologic grading, however, histologic grading may be subjective with high inter-observer variability. In this paper, we present histologic grading system and clinicopathological and radiological findings of conventional CHS. Subtypes of CHSs, such as dedifferentiated, mesenchymal, and clear cell CHSs are also presented. In addition, we introduce updated cytogenetic and molecular genetic findings to expand our understanding of CHS biology. New markers of cell differentiation, proliferation, and cell signaling might offer important therapeutic and prognostic information in near future

Molecular Basis of Lysosomal Enzyme Recognition: Three-Dimensional Structure of the Cation-Dependent Mannose 6-Phosphate Receptor

AbstractTargeting of newly synthesized lysosomal hydrolases to the lysosome is mediated by the cation-dependent mannose 6-phosphate receptor (CD-MPR) and the insulin-like growth factor II/cation-independent mannose 6-phosphate receptor (IGF-II/CI-MPR). The two receptors, which share sequence similarities, constitute the P-type family of animal lectins. We now report the three-dimensional structure of a glycosylation-deficient, yet fully functional form of the extracytoplasmic domain of the bovine CD-MPR (residues 3–154) complexed with mannose 6-phosphate at 1.8 Å resolution. The extracytoplasmic domain of the CD-MPR crystallizes as a dimer, and each monomer folds into a nine-stranded flattened β barrel, which bears a striking resemblance to avidin. The distance of 40 Å between the two ligand-binding sites of the dimer provides a structural basis for the observed differences in binding affinity exhibited by the CD-MPR toward various lysosomal enzymes