Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Experiment Videos

5-Aminolaevulinic acid dehydratase: structure, function, and mechanism.

D Shemin

    Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
    |February 5, 1976
    PubMed
    Summary

    Delta-Aminolaevulinic acid dehydratase, crucial for porphobilinogen synthesis, shows half-site reactivity. This enzyme remains active even when dissociated into smaller subunits, challenging previous assumptions about its structure and function.

    Related Concept Videos

    You might also read

    Related Articles

    Articles linked to this work by shared authors, journal, and citation graph.

    Sort by
    Same author

    Studies on the formation of heme and on the average life time of the human red blood cell.

    Federation proceedings·2010
    Same author

    The isotope dilution method of amino acid analysis.

    Annals of the New York Academy of Sciences·2010
    Same author

    The metabolism of proteins and amino acids.

    Annual review of biochemistry·2010
    Same author

    The biological conversion of l-serine to glycine.

    The Journal of biological chemistry·2010
    Same author

    The application of the isotope technique to the study of the rates of formation of blood constituents in man.

    The Journal of clinical investigation·2010
    Same author

    The biological utilization of glycine for the synthesis of the protoporphyrin of hemoglobin.

    The Journal of biological chemistry·2010

    Area of Science:

    • Biochemistry
    • Enzymology
    • Protein Structure

    Background:

    • Delta-Aminolaevulinic acid dehydratase (ALAD) catalyzes a key step in porphyrin biosynthesis, synthesizing porphobilinogen.
    • The enzyme is a large, multimeric protein with a molecular mass of approximately 285,000 Da, composed of eight identical subunits.

    Purpose of the Study:

    • To investigate the subunit arrangement and symmetry of delta-Aminolaevulinic acid dehydratase.
    • To explore the enzyme's active sites, cofactor requirements, and catalytic mechanism.
    • To determine the enzyme's stability and activity upon subunit dissociation.

    Main Methods:

    • Crystallization of the bovine liver enzyme.
    • Tryptic digestion to analyze peptide composition.
    • Enzyme reactivation studies with metal ions (zinc, cadmium).
    • Investigation of active thiol groups and substrate binding via Schiff base formation.
    • Enzyme immobilization and dissociation studies.

    Main Results:

    • The eight subunits exhibit dihedral (D4) symmetry, arranged cubically.
    • The enzyme contains 4-6 zinc atoms per mole and can be reactivated by zinc or cadmium.
    • Two highly active sulfhydryl groups per subunit are involved in catalysis.
    • Substrate binding suggests half-site reactivity or negative cooperativity, with only four subunits forming Schiff bases.
    • Immobilized enzyme remained stable and active after dissociation into tetramers, retaining 50% activity.

    Conclusions:

    • Delta-Aminolaevulinic acid dehydratase displays unique half-site reactivity, with only four of the eight subunits actively binding substrate.
    • The enzyme maintains catalytic activity even when dissociated into smaller oligomeric forms, indicating functional flexibility.
    • Strong subunit interactions are present, but the enzyme is functional as a tetramer, suggesting a revised understanding of its quaternary structure requirements.

    Related Experiment Videos