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Inhibition of Rhizopus lactate dehydrogenase by fructose 1,6-bisphosphate ☆

Paper ID Volume ID Publish Year Pages File Format Full-Text
17601 42682 2009 6 PDF Available
Title
Inhibition of Rhizopus lactate dehydrogenase by fructose 1,6-bisphosphate ☆
Abstract

The closely related fungi Rhizopus oryzae and Rhizopus delemar are often used for the production of lactic and fumaric acid, respectively. These organisms differ primarily by their ability to regenerate NAD through alternative fermentative routes. R. oryzae contains an NAD-dependent l-lactate dehydrogenase enzyme, RO-LdhA, that is primarily responsible for production of lactic acid, while both organisms contain another enzyme, LdhB that is thought to be involved in lactic acid production only under certain growth conditions. We have characterized LdhB from both R. oryzae and R. delemar, respectively referred to as RO-LdhB and RD-LdhB in this study, and have determined that RO-LdhB is significantly more effective than RD-LdhB with regard to kcat/Km with reductive LDH activity. Only negligible oxidative LDH activity could be measured with both enzymes; however, the presence of an amino terminal fusion with a small ubiquitin-related modifier, SUMO, increased the oxidative activity per μmol protein by more than 100-fold, while having little effect on the reductive LDH activity. We also determined that RO-LdhA, RO-LdhB, and RD-LdhB were all significantly inhibited in a non-competitive manner by fructose 1,6-bisphosphate (FBP) with Ki values of 1.2, 3.2, and 28.8 mM. Intracellular concentrations of FBP were tested with fermentative conditions to demonstrate that this metabolic intermediate does accumulate to levels that would likely cause inhibition of the R. oryzae LDH. Possible reasons for the significant Ki differences between the nearly identical LdhB proteins are discussed.

Keywords
Rhizopus oryzae; Lactate dehydrogenase; Fructose 1,6-bisphosphate
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Inhibition of Rhizopus lactate dehydrogenase by fructose 1,6-bisphosphate ☆
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 44, Issue 4, 6 April 2009, Pages 242–247
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us