Lactate Dehydrogenase (LDH) from Porcine Heart, 350 U/mg – Catalog #B2026857

Lactate Dehydrogenase (LDH; EC 1.1.1.27) from porcine heart (Catalog #B2026857) is supplied as 1 kU of enzyme in solution with a specific activity of 350 U/mg. LDH catalyzes the reversible interconversion of pyruvate and L-lactate with concomitant oxidation or reduction of NADH/NAD⁺. Because the reaction can be followed directly by the change in NADH absorbance at 340 nm, porcine heart LDH is widely used as a coupling enzyme in enzyme kinetics, metabolic assays, and teaching laboratories.

Scientific Overview

LDH is a tetrameric enzyme built from ~35 kDa subunits. In vertebrates, M-type (muscle) and H-type (heart) subunits assemble into isozymes with distinct kinetic and physicochemical properties. Heart tissue is dominated by the H-type isozyme (H4, LDH-1), and the three-dimensional structure of pig heart H4 LDH was one of the first dehydrogenase structures to be solved and correlated with isozyme sequence differences. The enzyme catalyzes:

Pyruvate + NADH + H⁺ ⇌ L-Lactate + NAD⁺

Because NADH absorbs strongly at 340 nm (ε ≈ 6,220 M⁻¹cm⁻¹) and NAD⁺ does not, LDH turns any reaction that produces pyruvate into a simple, continuous spectrophotometric readout. The most common example is the pyruvate kinase/LDH (PK/LDH) coupled assay, where ADP produced by an ATPase or kinase is recycled by pyruvate kinase and the resulting pyruvate is reduced by LDH.

Key applications include:

• Coupling enzyme for continuous NADH-linked assays (PK/LDH ATPase and kinase assays)
• Enzymatic determination of pyruvate or L-lactate
• Steady-state enzyme kinetics and teaching laboratory exercises
• Comparative studies of H- and M-type LDH isozymes

Usage & Handling Guidance

Store at −20°C as supplied. Thaw on ice, mix gently (do not vortex), and keep on ice during use. Dilute into cold assay buffer immediately before use and prepare aliquots to avoid repeated freeze–thaw cycles.

• Detection: Follow NADH oxidation or formation at 340 nm.
• Coupled assays: Supply LDH in sufficient excess that it is never rate-limiting; confirm by showing the observed rate does not change when LDH is increased.
• Unit definition: Unit definitions differ between suppliers (temperature, pH, direction of reaction). Request the COA/TDS for the lot-specific definition before converting units to mass.

What You Get

• 1 kU of Lactate Dehydrogenase from porcine heart, supplied in solution
• Specific activity of 350 U/mg
• A convenient working quantity for assay development and routine coupled assays
• For research use only (RUO)

Why Researchers Choose It

• High specific activity for use as a non-rate-limiting coupling enzyme
• Well-characterized heart (H-type) enzyme with decades of structural and kinetic literature
• Simple 340 nm readout compatible with standard spectrophotometers and plate readers
• Ready-to-use solution format

Frequently Asked Questions (FAQ)

• What reaction does LDH catalyze?
  The reversible reduction of pyruvate to L-lactate using NADH, producing NAD⁺.
• How is LDH used in a PK/LDH coupled assay?
  Pyruvate kinase converts ADP and phosphoenolpyruvate to ATP and pyruvate; LDH then reduces the pyruvate while oxidizing NADH, so ATP hydrolysis is read as a decrease in absorbance at 340 nm.
• Why porcine heart LDH rather than muscle LDH?
  Heart tissue provides mainly the H-type (LDH-1) isozyme, which differs kinetically from the muscle (M-type) form. Choose the isozyme that matches your assay conditions or the published method you are following.
• How should I store it?
  At −20°C. Aliquot to avoid repeated freeze–thaw cycles and keep on ice while working.
• Can I get a COA or TDS?
  Yes. Request a quote or contact us and we will provide available lot documentation.

References

• Eventoff W, Rossmann MG, Taylor SS, Torff HJ, Meyer H, Keil W, Kiltz HH. Structural adaptations of lactate dehydrogenase isozymes. Proc Natl Acad Sci U S A. 1977;74(7):2677-2681.
• Eventoff W, Hackert ML, Rossmann MG. A low-resolution crystallographic study of porcine heart lactate dehydrogenase. J Mol Biol. 1975;98(1):249-258.
• Grau UM, Trommer WE, Rossmann MG. Structure of the active ternary complex of pig heart lactate dehydrogenase with S-lac-NAD at 2.7 Å resolution. J Mol Biol. 1981;151(2):289-307.
• Kiltz HH, Keil W, Griesbach M, Petry K, Meyer H. The primary structure of porcine lactate dehydrogenase: isoenzymes M4 and H4. Hoppe Seylers Z Physiol Chem. 1977;358(1):123-127.
• Cahn RD, Zwilling E, Kaplan NO, Levine L. Nature and Development of Lactic Dehydrogenases: The two major types of this enzyme form molecular hybrids which change in makeup during development. Science. 1962;136(3520):962-9.
• Read JA, Winter VJ, Eszes CM, Sessions RB, Brady RL. Structural basis for altered activity of M- and H-isozyme forms of human lactate dehydrogenase. Proteins. 2001;43(2):175-185.