Molecular weight and tertiary structure of transketolase from baker's yeast]

Molecular weight of native apotransketolase from baker's yeast is found to be 159000 +/- 6000 by means of sedimentation equilibrium and sedimentation-diffusion rate. The enzyme in a relatively low concentration reversibly dissociates into two subunits with molecular weight of about 80 000 at pH 7.6 and 20 degrees C. The equilibrium constant of the reaction monomer-dimer is 4.4 . 10(3) M-1. A decrease of the temperature stimulates the association of monomers into dimer, while the shift of pH 7.6 into acid or alkaline region stimulates the dissociation process. Dissociation becames irreversible at pH less than 5 and greater than 10.5.     

Active subunits of transketolase from baker's yeast.

Transketolase from baker's yeast was covalently bound to Sepharose via one subunit. Storage in glycine buffer pH 11 entailled loss of half of the protein and a 50% decrease in the activity of the immobilized enzyme. Addition to the system of free subunits of transketolase doubled the amount of the protein attached to the matrix and restored the catalytic activity to the initial level. Thermoinactivation of the initial immobilized dimer of transketolase and the renatured dimer formed on reassociation of the immobilized subunits with the free ones was the same and considerably differed from the thermoinactivation of the immobilized subunits. The conclusion is made that the individual subunits of transketolase are catalytically active.     

Purification of transketolase from baker's yeast by an immunoadsorbent

Baker's yeast transketolase has been purified by immunoaffinity chromatography on specific TK antibodies covalently linked to CNBr-agarose. Affinity chromatography allows a 480-fold purification of TK from yeast extracts and about 80% recovery of the original activity. The isolated enzyme has a specific activity of 12-60 U/mg and during polyacrylamide gel electrophoresis performed at pH 8.9 migrates as two protein bands possessing a transketolase activity which corresponds to two isoforms of the enzyme.     

A new form of baker's yeast transketolase. An enzyme-RNA complex

Using an immunosorbent, a new form of transketolase, namely, an enzyme-RNA complex, was isolated from a baker's yeast extract. Spontaneous fission of RNA (or its enzymic hydrolysis by RNase) is accompanied by a sharp increase in the catalytic activity of transketolase, which may be directly related to the enzyme's regulation mechanism.     

A new method of isolation and a new form of transketolase from baker's yeast]

A new procedure for the isolation of homogeneous transketolase from baker's yeast based on the use of enzyme-specific antibodies immobilized on a insoluble matrix has been developed. The enzyme yield is 90% of its total content in the original yeast extract. The eluate from the immunocolumn was found to contain a previously unknown form of transketolase which represents an enzyme-RNA complex.     

The primary structure of tRNA Val 2a from baker's yeast]

The primary structure of tRNAVal2a from baker's yeast has been determined. The general methods of the investigation are presented. Twenty six distinguished points can be noted in the tRNAVal2a and tRNA1Val from baker's yeast. The anticodon region of tRNAVal2a is represented by the sequence NAC, where N corresponds to a uridine analogue nucleoside of unknown structure. The comparison of primary structures of tRNAVal2a, tRNAVal2a, tRNA1Val from E. coli and tRNAVal2a and tRNA1Val from baker's yeast is analysed.