Effect of flavins on the rate of proteolytic digestion of muscle glycogen phosphorylase b.
The kinetics of tryptic proteolysis of rabbit skeletal muscle phosphorylase b has been registered by the diminishing of protein fluorescence intensity at lambda = 335 nm (excitation at 290 nm) or by the disappearance of the enzyme activity (0.02 M Hepes buffer, pH 6.8, 37 degrees C). The first procedure showed that flavins (riboflavin, FMN, FAD) protected the enzyme against tryptic digestion. Microscopic dissociation constants for the complexes of phosphorylase b with riboflavin, FMN and FAD were calculated from dependences of the initial digestion rate on the flavin concentration. They where equal to 30 +/- 1, 15.8 +/- 0.2 and 36 +/- 1 microM, respectively. No influence of FMN on the rate of the tryptic hydrolysis of phosphorylase b was observed when using the second procedure (enzyme activity test). FMN completely prevents the formation of 69-, 81- and 85-kDa fragments during 20 min incubation of phosphorylase b with trypsin.
Kurganov
B I
BI
AN Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow.
Schors
E I
EI
Livanova
N B
NB
Chebotareva
N A
NA
Eronina
T B
TB
Andreeva
I E
IE
Makeeva
V P
VP
Pekel
N D
ND
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005486:Flavin Mononucleotide / Q000494:pharmacology; D005182:Flavin-Adenine Dinucleotide / Q000494:pharmacology; D005415:Flavins / Q000494:pharmacology*; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D010763:Phosphorylase b / Q000378:metabolism*; D011817:Rabbits; D012256:Riboflavin / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014357:Trypsin / Q000378:metabolism*; D014461:Ultracentrifugation
D005415:Flavins; D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide; D010763:Phosphorylase b; D014357:Trypsin; D012256:Riboflavin