113mIn radioisotope generator system

Al-Janabi, M. A. A.; Al-Hashimi, H. N.

doi:10.1007/bf02517930

Cited by 6 publications

(2 citation statements)

References 5 publications

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“…Hence the combined results of activation studies and the kinetic measurements indicated that in very acidic conditions the proteolytic cleavage of the prosegment represents a limiting step in the conversion of fusion protein to pepsin. The findings are consistent with observations of Al-Janabi et al (1972) and Glick et al (1986Glick et al ( , 1989) that the activation rates are pH dependent.…”

Section: Resultssupporting

confidence: 93%

“…First-order rate constants were calculated for each enzyme and are presented in Table III. Consistent with previous results (Al-Janabi et al, 1972;Tanaka and Yada, 1997), the reactions were the fastest at pH 1.1, intermediate at pH 2.0 and the slowest at pH 3.0 for all the enzymes. The activation process was similar, within experimental error, for the wild-type and T77S under all pH conditions.…”

Section: Resultssupporting

confidence: 92%

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The role of the flap residue, threonine 77, in the activation and catalytic activity of pepsin A

Okoniewska

Tanaka

Yada

1999

Protein Engineering, Design and Selection

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Flexible loops, often referred to as flaps, have been shown to play a role in catalytic mechanisms of different enzymes. Flaps at the active site regions have been observed in the crystal structures of aspartic proteinases and their residues implicated in the catalytic processes. This research investigated the role of the flap residue, threonine 77, in the activation of pepsinogen and the catalytic mechanism of pepsin. Three mutants, T77S, T77V and T77G, were constructed. Differences in amino acid polarity and hydrogen bonding potential were shown to have an influence on the activation and catalytic processes. T77S activated at the same rate and had similar catalytic parameters as the wild-type pepsin. The activation rates of T77V and T77G were slower and their catalytic efficiencies lower than the wild-type. The results demonstrated that the threonine 77 polar side chain played a role in a proteolysis. The contribution of the side chain to zymogen activation was associated with the proteolytic cleavage of the prosegment. It was postulated that the hydroxyl group at position 77 provided an essential hydrogen bond that contributed to proper substrate alignment and, indirectly, to a catalytically favorable geometry of the transition state.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 92%