Some properties of the leucine-biosynthesizing enzymes from Candida maltosa

✍ Scribed by Doz. Dr. Rüdiger Bode; Dieter Birnbaum

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 424 KB
• Volume: 31
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/jobm.3620310104

✦ Synopsis

The enzymes of the leucine pathway of Candida maltosa were investigated and the regulatory pattern was established. L-leucine inhibited the a-isopropylmalate (IPM) synthase, the first enzyme of the pathway. The inhibition was competitive with respect to a-ketoisovalerate , (Ki = 0.81 mM) and non-competitive with respect to acetyl-CoA. The K , values of the enzyme were estimated to be 0.57 mM for a-ketoisovalerate and 0.064mM for acetyl-CoA. The K , values of the second enzyme, IPM dehydratase, were estimated to be 4.57, 0.75 and 1.79 for a-IPM, P-IPM and citraconate, respectively. The K , values of the P-IPM dehydrogenase were calculated to be 0.42 mM for P-IPM and 0.34 mM for NAD+. For this enzyme a novel regulatory pattern, its inhibition by L-valine, was found. The inhibition was competitive with respect to 1-IPM (Ki = 1.7 mM) and non-competitive with respect to NAD'.