Rationally engineered variants of S-adenosylmethionine (SAM) synthase: reduced product inhibition and synthesis of artificial cofactor homologues.

S-Adenosylmethionine (SAM) synthase was engineered for biocatalytic production of SAM and long-chain analogues by rational re-design. Substitution of two conserved isoleucine residues extended the substrate spectrum of the enzyme to artificial S-alkylhomocysteines. The variants proved to be beneficial in preparative synthesis of SAM (and analogues) due to a much reduced product inhibition.

[Na K ATPase activity in rat kidneys following storage at 4 degrees C in various kidney preservative solutions]. / NA-K-ATPase-Aktivität in Rattennieren nach Lagerung bei 4 degrees C in verschiedenen Nierenkonservierungslösungen.

The Na-K-ATPase is the enzymatic basis of a energy-dependent transport of sodium and potassium through the cell membrane and is therefore of importance to the survival of organs during periods of decreased energy supply. In the present paper the influence of various preservation solutions on the activity of this enzyme was examined. It was shown that Na-K-ATPase activity in rat kidneys did remain unchanged after 48 hour preservation in various preservation solutions (Bretschneider, Ross, Collins, Sacks, Belzer). Therefore, its estimation is no valuable for evaluation of preservation solutions.