Abstract
The present study was conducted to investigate a new pathway for the degradation of nicotinamide adenine dinucleotide (NAD) by Penicillium brevicompactum NRC 829 extracts. Enzymes involved in the hydrolysis of NAD, i.e. alkaline phosphatase, aminohydrolase and glycohydrolase were determined. Alkaline phosphatase was found to catalyse the sequential hydrolysis of two phosphate moieties of NAD molecule to nicotinamide riboside plus adenosine. Adenosine was then deaminated by aminohydrolase to inosine and ammonia. While glycohydrolase catalyzed the hydrolysis of the nicotinamide-ribosidic bond of NAD+ to produce nicotinamide and ADP-ribose in equimolar amounts, enzyme purification through a 3-step purification procedure revealed the existence of two peaks of alkaline phosphatases, and one peak contained deaminase and glycohydrolase activities. NAD deaminase was purified to homogeneity as estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis with an apparent molecular mass of 91 kDa. Characterization and determination of some of NAD aminohydrolase kinetic properties were conducted due to its biological role in the regulation of cellular NAD level. The results also revealed that NAD did not exert its feedback control on nicotinamide amidase produced by P. brevicompactum.
Highlights
Increasing evidences have indicated that nicotinamide adenine dinucleotide (NAD) and NADH play critical roles in energy metabolism, and in several cellular functions including calcium homeostasis, gene expression, ageing, immunological mechanisms and cell death (Leonarda 2008)
Penicillium brevicompactum NRC 829 extracts were incubated with NAD at different pH values
These enzymes are similar in being orthophosphate- non repressible enzymes and being not true phosphomonoesterases. This last property was based on their abilities to catalyse the hydrolysis of pyrophosphate linkage of ADP and the internal ester linkage between nicotinamide riboside (NR) and ADP, in addition to the true phosphate ester linkages of NAD, ADP and adenosine 50-monophosphate (AMP)
Summary
Increasing evidences have indicated that NAD and NADH play critical roles in energy metabolism, and in several cellular functions including calcium homeostasis, gene expression, ageing, immunological mechanisms and cell death (Leonarda 2008). Alkaline phosphatases involved in NAD degradation which cleave NAD at the phosphate linkage to produce ADP and nicotinamide riboside have been characterized earlier in our laboratory from A. niger (Elzainy and Ali 2000), A. terreus (Elzainy and Ali 2003, 2005). AMP was further cleaved by the same enzyme to produce adenosine plus Pi. Non-specific degradation of NAD to nicotinamide riboside was detected in Escherichia coli (Wang et al 2014). Adenosine deaminase of Aspergillus oryzae (Ali et al 2012, 2014) has been characterized in our laboratory Both the adenosine and by-products of the NAD-consuming enzymes such as NMN and Nm can be recycled back to NAD (Sorcil et al 2010; Gazzaniga et al 2009). NAD aminohydrolase was purified to homogeneity and some of kinetic properties were characterized
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
