Cellobiose phosphorylase (CBP) catalyzes the reversible phosphorolysis of cellobiose to produceD -glucopyranosyl phosphate (Glc1P) and D-glucose. It is an essential enzyme for the metabolism of cello-oligosaccharides in a ruminal bacterium, Ruminococcus albus. In this study, recombinant R. albus CBP (RaCBP) produced in Escherichia coli was characterized. It showed highest activity at pH 6.2 at 50 C, and was stable in a pH range of 5.5-8.8 and at below 40 C. It phosphorolyzed only cellobiose efficiently, and the reaction proceeded through a random-ordered bi bi mechanism, by which inorganic phosphate and cellobiose bind in random order and D-glucose is released before Glc1P. In the synthetic reaction, RaCBP showed highest activity to D-glucose, followed by 6-deoxy-Dglucose. D-Mannose, 2-deoxy-D-glucose, D-glucosamine, D-xylose, 1,5-anhydro-D-glucitol, and gentiobiose also served as acceptors, although the activities for them were much lower than for D-glucose. D-Glucose acted as a competitive-uncompetitive inhibitor of the reverse synthetic reaction, which bound not only the Glc1P site (competitive) but also the ternary enzyme-Glc1P-Dglucose complex (uncompetitive).

Unbiased understanding of molecular distributions in a disk/envelope system of a low-mass protostellar source is crucial for investigating physical and chemical evolution processes. We have observed 23 molecular lines toward the Class 0 protostellar source L483 with ALMA and have performed principal component analysis (PCA) for their cube data (PCA-3D) to characterize their distributions and velocity structures in the vicinity of the protostar. The sum of the contributions of the first three components is 63.1%. Most oxygen-bearing complex organic molecule lines have a large correlation with the first principal component (PC1), representing the overall structure of the disk/envelope system around the protostar. Contrary, the C18O and SiO emissions show small and negative correlations with PC1. The NH2CHO lines stand out conspicuously at the second principal component (PC2), revealing more compact distribution. The HNCO lines and the high-excitation line of CH3OH have a similar trend for PC2 to NH2CHO. On the other hand, C18O is well correlated with the third principal component (PC3). Thus, PCA-3D enables us to elucidate the similarities and the differences of the distributions and the velocity structures among molecular lines simultaneously, so that the chemical differentiation between the oxygen-bearing complex organic molecules and the nitrogen-bearing ones is revealed in this source. We have also conducted PCA for the moment 0 maps (PCA-2D) and that for the spectral line profiles (PCA-1D). While they can extract part of characteristics of the molecular line data, PCA-3D is essential for comprehensive understandings. Characteristic features of the molecular line distributions are discussed on NH2CHO.

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract