Studies on degradation of adenosine-5′-phosphosulphate (APS) and adenosine-3′-phosphate-5′-phosphosulphate (PAPS) in extracts of Anabaena cylindrica

A new method of sequencing DNA

An entirely new method of sequencing DNA has been devised that does not use electrophoresis, radioactivity, or fluorescence. The method works by measuring pyrophosphate generated by the DNA polymerization reaction. DNA and DNA polymerase are held by a DEAE-Sepharose column and solutions containing different dNTPs are pumped through. The pyrophosphate generated is measured continuously by a device consisting of a series of columns containing enzymes covalently attached to Sepharose. The alternating copolymer poly(dA.dT) is sequenced as an illustration of the method. Future improvements that will facilitate automation are discussed.

Adenosine 5'-triphosphate sulphurylase from Spirulina platensis

ATP-sulphurylase from an unicellular blue-green alga, Spirulina platensis was localized in the soluble fractions of cell-free homogenate, and it was stable for over 3 weeks at -6 degrees C.

Activation of sulphate in Anabaena cylindrica

Crude cell-free extracts of Anabaena cylindrica synthesized adenosine-5'-phosphosulphate (AP(35)S) and 3'-phosphoadenosine-5'-phosphosulphate (PAP(35)S) from (35)SO4 (2-) in the presence of Mg(2+), ATP and inorganic pyrophosphatase. Maximum AP(35)S and PAP(35)S were produced at pH 7.15 and 8.05, respectively. APS kinase was detected in the supernatant of crude cell-free extracts by a spectrophotometric procedure. ATP-Sulphurylase had an absolute requirement for Mg(2+) and less than 30% AP(35)S was formed when Mg(2+) was replaced by either Mn(2+) or Co(2+). Nucleotide triphosphates other than ATP and 2'-deoxyATP were ineffective in this reaction. Maximum enzyme activity was observed at equimolar concentrations of Mg(2+) and ATP and excess of either of these was inhibitory. Other nucleotide triphosphates, like GTP, UTP, CTP, TTP, ITP, or 2'-deoxyATP also inhibited the enzyme activity. Inhibition by GTP was competitive with respect to ATP. ATP-sulphurylase activity was not affected by cysteine, methionine or glutathione.