Several classes of biological reactions that are mediated by an enzyme and a co-factor can occur, to a slower extent, not only without the enzyme but even without the co-factor, under catalysis by metal ions. This observation has led to the proposal that metabolic pathways progressively evolved from using inorganic catalysts to using organocatalysts of increasing complexity. Transamination, the biological process by which ammonia is transferred between amino acids and keto acids, has a mechanism that has been well studied under enzyme/co-factor catalysis and under co-factor catalysis, but the metal ion-catalyzed variant was generally studied mostly at high temperatures (70-100 ºC), and the details of its mechanism remain unclear. Here, we investigate which metal ions catalyze transamination under conditions relevant to biology (pH 7, 20-50 ºC) and study the mechanism in detail. Cu 2+ , Ni 2+ , Co 2+ and V 5+ were identified as the most active metal ions under these constraints. Kinetic, stereochemical and computational studies illuminate the mechanism of the reaction. Cu 2+ and Co 2+ are found to predominantly speed up the reaction by stabilizing a key imine intermediate. V 5+ is found to accelerate the reaction by increasing the acidity of the bound imine. Ni 2+ is found to do both to a limited extent. These results show that direct metal ion-catalyzed amino group transfer is highly favored even in the absence of cofactors or protein catalysts under biologically compatible reaction conditions.

Aim:The aim of this study is to compare the antiplaque efficacy of green tea catechin mouthwash with chlorhexidine gluconate mouthwash.Materials and Methods:A single blinded cross-over study was conducted among 30 participants in the age group of 18-25 years. The mouthwash samples for the study were previously labeled assigning the letters: A (0.25% of green tea catechin mouthwash) and B (0.12% of chlorhexidine mouthwash). The study subjects were randomly divided into two groups of 15 each and the study was divided into two phases. In phase I, the mouthwash A was given to one group and other group was given mouthwash B. After a 15 day washout period, in phase II, both groups were given other mouthwash. At the end of each phase of 1 week, plaque score was recorded by using Turesky modification of the Quigley-Hein plaque index.Results:The plaque scores were compared and the difference between the green tea catechin and chlorhexidine mouthwash was determined by t-test. The difference between plaque scores were not statistically significant (P > 0.05). The results showed that both the groups that is green tea catechin mouthwash (0.25%) and chlorhexidine mouthwash (0.12%) have comparable results in plaque reduction.Conclusion:This study supports the effectiveness of green tea catechin mouthwash as an antiplaque agent. It should be explored as a cost-effective, long-term antiplaque rinse with prophylactic benefits.

Metabolic theories for the origin of life posit that inorganic catalysts enabled self‐organized chemical precursors to the pathways of metabolism, including those that make genetic molecules. Recently, experiments showing nonenzymatic versions of a number of core metabolic pathways have started to support this idea. However, experimental demonstrations of nonenzymatic reaction sequences along the de novo ribonucleotide biosynthesis pathways are limited. Here we show that all three reactions of pyrimidine nucleobase biosynthesis that convert aspartate to orotate proceed at 60 °C without photochemistry under aqueous conditions in the presence of metals such as Cu2+ and Mn4+. Combining reactions into one‐pot variants is also possible. Life may not have invented pyrimidine nucleobase biosynthesis from scratch, but simply refined existing nonenzymatic reaction channels. This work is a first step towards uniting metabolic theories of life's origin with those centered around genetic molecules.