Tushar Kanti Maiti

Copper complexes of ( )-epicatechin gallate and ( )-epigallocatechin gallate act as inhibitors of Ribonuclease A

Green tea polyphenols, which have the ability to inhibit angiogenesis, form complexes with Cu(II), a known potent stimulator of blood vessel proliferation. Copper complexes of (−)‐epicatechin gallate and (−)‐epigallocatechin gallate were found to inhibit the enzymatic activity of Ribonuclease A (RNase A) as revealed by an agarose gel based assay and urea denatured gel electrophoresis. The copper complexes were found to be non‐competitive inhibitors of RNase A with inhibition constants in the micromolar range. Changes in the secondary structure of the protein are found to occur due to the interaction as revealed from Fourier transform infrared and circular dichroism studies.

Effect of green tea polyphenols on angiogenesis induced by an angiogenin-like protein

Angiogenesis is a fundamental process by which new blood vessels are formed. The angiogenesis process is induced by several growth factors. Among them angiogenin is the most potent blood vessel inducer known. In this paper, we have investigated the effect of green tea polyphenols, mainly the catechins, on an angiogenin-like protein induced angiogenesis process. The angiogenin-like protein was isolated from goat serum and the effect of green tea components was tested by the chicken chorioallantoic membrane (CAM) assay. The results show that green tea components are capable of reducing the vascularization on CAM that is induced by the angiogenin-like protein.

Inhibition of Ribonuclease A by polyphenols present in green tea

We report the effect of the natural polyphenolic compounds from green tea on the catalytic activity of Ribonuclease A (RNase A). The compounds behave as noncompetitive inhibitors of the protein with inhibition constants ranging from 80–1300 μM. The dissociation constants range from 50–150 μM for the RNase A–polyphenol complexes as determined by ultraviolet (UV) and circular dichroism (CD) studies. We have also investigated the changes in the secondary structure of RNase A on complex formation by CD and Fourier transformed infrared (FTIR) spectroscopy. The presence of the gallate moiety has been shown to be important for the inhibition of enzymatic activity. Docking studies for these compounds indicate that the preferred site of binding is the region encompassing residues 34–39 with possible hydrogen bonding with Lys 7 and Arg 10. Finally we have also looked at changes in the accessible surface area of the interacting residues on complex formation for an insight into the residues involved in the interaction. Proteins 2007.

Isolation and Characterization of an Angiogeninlike Protein from Goat Plasma

Angiogenin, a blood vessel inducing protein has been implicated in wound healing and tumour progression. First isolated from human carcinoma cells, it has been subsequently isolated from human, bovine, rabbit, pig and mouse sera and bovine milk. This study reports the isolation of an angiogenic-like protein from goat plasma. The ribonucleolytic activity has been followed by yeast transfer RNA (tRNA) degradation using spectrophotometric and denaturing polyacrylamide gel electrophoresis methods. The chorioallantoic membrane (CAM) assay has been implemented to study its angiogenic activity. The presence of this protein has also been confirmed by strong binding with placental Ribonuclease Inhibitor (PRI).

Isolation and Partial Characterization of Ribonuclease Inhibitor from Goat Liver

Ribonuclease inhibitor (RI), a 50 kDa protein, has been found both in mammalian and nonmammalian tissues. We have isolated RI from goat liver and partial characterization has been accomplished. For the isolation of RI, DEAE cellulose column chromatography followed by affinity chromatography using CNBr activated Sepharose 4B was performed. The inhibition of ribonucleolytic activity of Ribonuclease A has been checked by an agarose gel based assay. The antiangiogenic property of the protein was tested by the chorioallantoic membrane (CAM) assay. Results indicate inhibition of angiogenesis.