Key result
Renin strongly inhibits renin-binding protein GlcNAc 2-epimerase activity by forming an inactive heterodimer.
Why the study?
The inhibitory effect of renin on human N-acetyl-D-glucosamine 2-epimerase activity mediated by renin-binding protein was not fully characterized.
Renin and renin-binding protein (GlcNAc 2-epimerase) mutually inhibit each other's enzymatic activities by forming a heterodimer.
Caution against inferring clinical effects from this biochemical interaction; leaves open a regulatory link between renin and carbohydrate metabolism for further study.
Renin-binding protein (RnBP) is a highly specific renin inhibitor first isolated from porcine kidney. Our recent studies demonstrated that the human RnBP is the enzyme N-acetyl-D-glucosamine (GlcNAc) 2-epimerase [Takahashi, S. et al. (1999) J. Biochem. 125, 348-353]. We have developed a new assay method for GlcNAc 2-epimerase activity using a system of N-acyl-D-hexosamine oxidase coupled with peroxidase and employed this method to study the effects of renin on GlcNAc 2-epimerase activity. The recombinant human (rh) RnBP existed as a dimer and its GlcNAc 2-epimerase activity was strongly inhibited by the purified renin concomitant with the formation of RnBP-renin heterodimer, so-called high molecular weight (HMW) renin. The renin activity was also inhibited by rhRnBP in a dose-dependent manner. These results indicate that renin is an inhibitor of GlcNAc 2-epimerase, and the renin-RnBP heterodimer HMW renin is an inactive form of both renin and GlcNAc 2-epimerase activities.
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Takahashi et al. (2000) studied this question. Renin was evaluated on GlcNAc 2-epimerase activity. Renin strongly inhibited the GlcNAc 2-epimerase activity of recombinant human renin-binding protein, forming an inactive heterodimer.
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