Braunstein-Snell hypothesis

Pyridoxal phosphate and its close relative, pyridoxamine phosphate (Fig. 1, 6) participate in a multiplicity of different biological processes, most noteworthy amongst these being the reaction involved in the metabolism of amino acids [3-6]. Several dozen enzymes are known whose activities are dependent on the presence of pyridoxal phosphate in their active sites. Our current view regarding the niechanisms of pyridoxal-P-dependent transformations is based on the inspired suggestion originally made in 1953, independently by Braunstein and Shemyakin [7] in the Soviet Union, and Snell and his coworkers [8] in the United States. Before considering the basic tenets of the Braunstein-Snell hypothesis we examine the nature of the chemical problems involved in the metabolism of amino acids. In the later sections we shall note that the key event in the metabolism of amino acids is either the... 

In the light of this background we consider an enormous body of experimental work on pyridoxal-P-dependent enzymic reactions which has accumulated since the enunciation of the Braunstein-Snell hypothesis. Broadly speaking, at a crucial stage in these reactions, the cleavage of either the C -COOH or C -H bond is involved. In Sections 2-5 transformations belonging to these two classes are discussed sequentially with major emphasis on the description of events which occur on the... 

A broad range of enzymic reactions of amino acids is mediated by pyridoxal phosphate (PLP), the cofactor form of vitamin Bg. The general mechanism of action of this cofactor was suggested independently by Braunstein and Shemyakin (16) and by Snell (17), and although a great deal of experimental work has been achieved since the Braunstein-Snell hypothesis was put forward, it still holds good today. 

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