Purification and properties of two forms of hepatic phenylalanine:pyruvate transaminase from glucagon treated rats.

Two forms of phenylalanine:pyruvate transaminase (EC 2.6.1. aminotransferases, the exact EC number has not been assigned) termed A and B were obtained from the liver supernatant fraction of glucagon-treated rats by DEAE-Sephadex A-50 column chromatography. Each of the two forms was further purified by hydroxylapatite, Sephadex G-100 chromatography, and preparative gel electrophoresis. Both the A and B forms have been purified to homogeneity as judged by analytical and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Moreover, histidine was found to be a competitive inhibitor of phenylalanine with both purified proteins. These findings conclusively support the view that phenylalanine:pyruvate transaminase and histidine:pyruvate transaminase reactions are catalyzed by the same protein. The overall purification was 710-fold for the A form and 1200-fold for the B form. The apparent molecular weight for both A and B are 74,000 ±6000 as determined by gel filtration. Sodium dodecyl sulfate gel electrophoresis revealed that the A form has two identical subunits of molecular weight 42,000, whereas the B form has two nonidentical subunits of molecular weight 42,000 and 44,000. The amino acid composition for the A and B forms of the enzyme are different. The major differences are in glycine, alanine and leucine. The isoelectric point for A was 7.8 and for B was 7.3. However, the A and B forms of the enzyme are of immunological identity. The substrate specificity determined for both the A and B form was phenylalanine >asparagine >alanine >leucine >histidine. The K_m for phenylalanine was 7.70 mm for the A form, 6.00 mm for the B form. For histidine, the K_m was 13.70 mm for the A form, 12.50 mm for the B form.     

Historical profiling of maize duplicate genes sheds light on the evolution of C4 photosynthesis in grasses

C4 plants evolved from C3 plants through a series of complex evolutionary steps. On the basis of the evolution of key C4 enzyme genes, the evolution of C4 photosynthesis has been considered a story of gene/genome duplications and subsequent modifications of gene function. If whole-genome duplication has contributed to the evolution of C4 photosynthesis, other genes should have been duplicated together with these C4 genes. However, which genes were co-duplicated with C4 genes and whether they have also played a role in C4 evolution are largely unknown. In this study, we developed a simple method to characterize the historical profile of the paralogs of a gene by tracing back to the most recent common ancestor (MRCA) of the gene and its paralog(s) and then counting the number of paralogs at each MRCA. We clustered the genes into clusters with similar duplication profiles and inferred their functional enrichments. Applying our method to maize, a familiar C4 plant, we identified many genes that show similar duplication profiles with those of the key C4 enzyme genes and found that the functional preferences of the C4 gene clusters are not only similar to those identified by an experimental approach in a recent study but also highly consistent with the functions required for the C4 photosynthesis evolutionary model proposed by S.F. Sage. Some of these genes might have co-evolved with the key C4 enzyme genes to increase the strength of C4 photosynthesis. Moreover, our results suggested that most key C4 enzyme genes had different origins and have undergone a long evolutionary process before the emergence of C4 grasses (Andropogoneae), consistent with the conclusion proposed by previous authors.     

Fossils from the Middle Jurassic of China shed light on morphology of Choristopsychidae (Insecta,Mecoptera)

Choristopsychidae, established by Martynov in 1937 with a single isolated forewing, is a little known extinct family in Mecoptera. Since then, no new members of this enigmatic family have been described. Based on 23 well-preserved specimens with complete body and wings from the Middle Jurassic of northeastern China, we report one new genus and three new species of Choristopsychidae, two new species of the genus Choristopsyche Martynov, 1937: Choristopsyche perfecta sp. n. and Choristopsyche asticta sp. n.; one new species of Paristopsyche gen. n.: Paristopsyche angelineae sp. n.; and re-describe Choristopsyche tenuinervis Martynov, 1937. In addition, we emend the diagnoses of Choristopsychidae and Choristopsyche. Analyzing the forewing length/width ratios of representative species in Mecoptera, we confirm that choristopsychids have the lowest ratio of forewing length/width, meaning broadest forewings. These findings, the first fossil choristopsychids with well-preserved body structure and the first record of Choristopsychidae in China, shed light on the morphology of these taxa and broaden their distribution from Tajikistan to China, while increasing the diversity of Mesozoic Mecoptera in China.     

Plant defense after flooding

Since the first study of hypoxic response in plants with cDNA microarray in 2002, the number of hypoxia-responsive genes has grown to more than 2000. However, to date, only small numbers of hypoxia-responsive genes are known to confer hypoxic resistance. Most investigations in this area have focused on identifying which genes are responsive and then characterized how these genes are induced during hypoxia, but the roles of numerous genes in hypoxic response are still unknown. In our recent study, we demonstrated that a group of genes are induced by submergence to trigger plant immunity, which is a response to protect plants against a higher probability of pathogen infection during or after flooding. This work offered a brand new perspective, i.e., that hypoxia-responsive genes can be induced for reasons other than conferring hypoxic resistance. Possible reasons why these responses were triggered are discussed herein.     

Surface α-Enolase Promotes Extracellular Matrix Degradation and Tumor Metastasis and Represents a New Therapeutic Target

In previous research, we found α-enolase to be inversely correlated with progression-free and overall survival in lung cancer patients and detected α-enolase on the surface of lung cancer cells. Based on these findings, we hypothesized that surface α-enolase has a significant role in cancer metastasis and tested this hypothesis in the current study. We found that α-enolase was co-immunoprecipitated with urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor, and plasminogen in lung cancer cells and interacted with these proteins in a cell-free dot blotting assay, which can be interrupted by α-enolase-specific antibody. α-Enolase in lung cancer cells co-localized with these proteins and was present at the site of pericellular degradation of extracellular matrix components. Treatment with antibody against α-enolase in vitro suppressed cell-associated plasminogen and matrix metalloproteinase activation, collagen and gelatin degradation, and cell invasion. Examination of the effect of treatment with shRNA plasmids revealed that down regulation of α-enolase decreases extracellular matrix degradation by and the invasion capacity of lung cancer cells. Adoptive transfer of α-enolase-specific antibody to mice resulted in accumulation of antibody in subcutaneous tumor and inhibited the formation of tumor metastasis in lung and bone. This study demonstrated that surface α-enolase promotes extracellular matrix degradation and invasion of cancer cells and that targeting surface α-enolase is a promising approach to suppress tumor metastasis.