Effects of kinase inhibitors and potassium phosphate (KPi) on site-specific phosphorylation of branched chain. cap alpha. -ketoacid dehydrogenase (BCKDH)

Conference · Fri May 01 00:00:00 EDT 1987 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6179702

Kuntz, M J; Shimomura, Y; Ozawa, T; Harris, R A

BCKDH is phosphorylated by a copurifying kinase at two serine residues on the El..cap alpha.. subunit. Phosphorylation of both sites occurs at about the same rate initially, but inactivation is believed associated only with site 1 phosphorylation. The effects of KPi and known inhibitors of BCKDH kinase, ..cap alpha..-chloroisocaproate (CIC) and branched chain ..cap alpha..-ketoacids (BCKA), on the phosphorylation of purified rat liver BCKDH were studied. Site-specific phosphorylation was quantitated by thin-layer electrophoresis of tryptic peptides followed by densitometric scanning of autoradiograms. Addition of 5 mM KPi was found necessary to stabilize the BCKDH activity at 37/sup 0/C. Increasing the KPi to 50 mM dramatically increased the CIC and BCKA inhibition of site 1 and site 2 phosphorylation. The finding of enhanced sensitivity of inhibitors with 50 mM KPi may facilitate identification of physiologically important kinase effectors. Regardless of the KPi concentration, CIC and the BCKA showed much more effective inhibition of site 2 than site 1 phosphorylation. Although site 1 is the primary inactivating site, predominant inhibition of site 2 phosphorylation may provide a means of modulating kinase/phosphatase control of BCKDH activity under steady state conditions.

• Research Organization: Indiana Univ. School of Medicine, Indianapolis
• OSTI ID: 6179702
• Report Number(s): CONF-870644-; TRN: 87-034025
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENZYME INHIBITORS
BIOCHEMICAL REACTION KINETICS
OXIDOREDUCTASES
ENZYME ACTIVITY
PHOSPHORYLATION
AUTORADIOGRAPHY
ELECTROPHORESIS
PHOSPHATES
POTASSIUM COMPOUNDS
STEADY-STATE CONDITIONS
ALKALI METAL COMPOUNDS
CHEMICAL REACTIONS
ENZYMES
KINETICS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
REACTION KINETICS
550201* - Biochemistry- Tracer Techniques