Mechanism of action of aspartate aminotransferase proposed on the basis of its spatial structure.

The structure of the bifunctional, pyridoxal phosphate-dependent enzyme dialkylglycine decarboxylase was determined to 2.1-angstrom resolution. Model building suggests that a single cleavage site catalyzes both decarboxylation and transamination by maximizing stereoelectronic advantages and providing electrostatic and general base catalysis. The enzyme contains two binding sites for alkali metal ions. One is located near the active site and accounts for the dependence of activity on potassium ions. The other is located at the carboxyl terminus of an alpha helix. These sites help show how proteins can specifically bind alkali metals and how these ions can exert functional effects.

https://science.sciencemag.org/content/sci/261/5122/756.full.pdf

Dialkylglycine Decarboxylase Structure: Bifunctional Active Site and Alkali Metal Sites

The relation of spectral changes and tritium exchange reactions to the mechanism of tryptophanase-catalyzed reactions.

Tyrosine Phenol Lyase I. PURIFICATION, CRYSTALLIZATION, AND PROPERTIES

The amino functionality gives important biological activity in pharmaceutical com-pounds. The formation of chiral amines and amino acids can be accomplished by seve-ral chemical routes but enzymatic formation of amines offers many advantages in pre-paring chiral amino compounds or amination of fragile compounds compared to stoi-chiometric or catalytic chemical transformations. Biocata- lytic routes to amines primarily use enzymes of the transaminase class (also known as aminotransferases) which transfer the amino func- tion from a donor organic compound to a ketone or aldehyde acceptor. Although known since 1937, the transamination reaction experi- ences re-newed interest due to the advances in biochemistry and molecular biology and the excellent selectivity of biocatalysts. Other en- zymes that have been used to synthesize chiral amines are from the phenylalanine ammonia lyase class that use ammonia as the amino source. The use of recombinant enzymes for the biocatalytic preparation of amines is expanding at a great rate and the range of enzymes revealed in DNA se-quence databases is of the order of tens of thousands. Since a large number of ketone substrates like ketones, hy- droxyketones and ketoacids can be made by chemical syn-thesis, the growing toolbox of � - , � -, � -, � -, � - and � -transaminases enable the synthe-sis of various new chemical entities by biocatalytic amination reactions. In order to simplify the isolation and purification of the product, it is useful to drive the amination reaction to completion. The biocatalytic processes that have been developed show different strategies of overcoming the kinetic limitations of the transaminase reactions and show how some enzymes have been used in processes to make large quantities of chiral compounds with amino functionalities.

A. E. Brattnshtbin

Papers

Theory of the process of amino-acid metabolism, catalysed by pyridoxal enzymes.