A novel potential metallopeptidase derived from the enkephalinase gene by alternative splicing

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Enkephalinase (EC 3.4.24.11, membrane metalloendopeptidase, MME I) is a key enzyme involved in neuropeptide metabolism.
• Understanding gene expression and protein variants is crucial for elucidating complex biological functions.

Purpose of the Study:

• To investigate the molecular mechanisms of enkephalinase gene expression in rat intestine.
• To identify and characterize novel transcripts and protein products derived from the enkephalinase gene.

Main Methods:

• Reverse transcriptase-polymerase chain reaction (RT-PCR) was employed to amplify rat intestine mRNAs.
• Oligonucleotide primers targeting the translated region of the enkephalinase (MME I) gene were utilized.
• mRNA sequencing and sequence analysis were performed to identify and characterize alternative splicing events.

Main Results:

• A shorter mRNA transcript, in addition to the expected enkephalinase (MME I) transcript, was identified.
• Sequence analysis revealed this shorter transcript results from the deletion of exons 5-18 of the MME I gene.
• This alternatively spliced mRNA encodes a novel protein, MME II (255 amino acids), distinct from the full-length enkephalinase (742 amino acids).
• The deduced structure of MME II suggests it is a membrane-bound, zinc-containing glycoprotein with altered peptidase activity.
• MME II mRNA expression was observed in brain and thyroid tissues, alongside MME I mRNA, indicating tissue-specific regulation.

Conclusions:

• Alternative splicing of the enkephalinase gene generates a novel protein variant, MME II, with potentially distinct functional properties.
• MME II represents a significant finding in the study of metalloendopeptidases and their regulation.
• The tissue-specific expression of MME II suggests specialized roles in different organs, warranting further investigation into its physiological functions.