Lactate Dehydrogenase

Lactate Dehydrogenase

EC 1.1.1.27; L-lactate: NAD+ oxidoreductase; LD)

Lactate dehydrogenase is a hydrogen transfer enzyme that catalyzes the oxidation of _____________ to _____________ with the mediation of ___________ as a hydrogen acceptor. The reaction is _____________ and the reaction equilibrium strongly favors the __________________, the reverse reaction.

L-lactate to pyruvate

NAD+

reversible,

reduction of pyruvate to lactate (P + L)

The LD enzyme has a molecular weight of ___________ and is composed of _____________ of two types: ______________, each under separate genetic control (______________, respectively).

134,000 Da

four peptide chains

M (or A) and H (or B)

chromosome 11 and 12

The subunit compositions of the five isoenzymes, in order of decreasing anodal mobility in an alkaline medium are:

LD-1 (HHHH, H4); LD-2 (HHHM; H3M); LD-3 (HHMM, H2M2); LD-4 (HMMM, HM3); and LD-5 (MMMM; M4)

In the sera of healthy individuals, the major isoenzyme fraction is ____________, followed by:

LD-2

LD1, LD-3, LD-4, and LD-5

There is a sixth LD isoenzyme, _____________, composed of _____________.

LD-X (also called LDc)

four X (or C) subunits

An isoenzyme present in post-pubertal human testes.

LD-X (also called LDc)

A seventh LD, called _______________, has been identified in the sera of patients with arteriosclerotic cardiovascular failure.

LD-6 (alcohol dehydrogenase)

_____________ may reflect liver injury secondary to severe circulatory insufficiency.

LDH-6

Lactate dehydrogenase in various tissues are about ________________ than those physiologically found in serum.

5000 times higher

Leakage of the enzyme from even a small mass of damaged tissue ____________________.

increases the observed serum activity of LD

LD elevations occur in a variety of clinical conditions with more relevance to _____________ and ________________.

hematological disorders and malignancies

_______________ and ____________________ contain higher concentration of LD-1.

Cardiac tissue and red blood cells

In conditions involving _________________, the serum levels of LD-1 will increase to a point at which they are present in greater concentration than LD2, resulting in a condition known as the ______________________.

cardiac necrosis (AMI) and intravascular hemolysis

LDH flipped pattern (LD-1 > LD-2)

LD is not specific to ______________ and is not a preferred marker of diagnosis of AMI.

cardiac tissue

In AMI, LD levels begin to rise within _______________, reach peak levels within ________________, and may remain elevated for ______________.

12 to 24 hours

48 to 72 hours

10 days

For AMI:

LD rise within 12-24 hrs

Peak at 48-72 hrs

Remain elevated for 10 days

Highest elevation of LD occurs in cases of ___________________, ___________________, ________________.

hemolytic anemia, pernicious anemia and megaloblastic anemia

____________, if sufficiently severe, produces an LD isoenzyme pattern similar to that in myocardial infarction.

Hemolysis

_________________ usually resulting from the deficiency of folate or vitamin B12, cause the erythrocyte precursor cell to break down in the bone marrow (ineffective erythropoiesis). This results to the release of large quantities of ________________ and __________________.

Megaloblastic anemias

LD-1 and LD- 2 isoenzymes

Since LD-3 are distributed in the spleen, lungs, lymph nodes, leukocytes and platelets, elevations also occur with ____________ and in patients with _______________ and various carcinomas, including _______________, __________________, _______________.

pulmonary involvement

infectious mononucleosis

acute lymphocytic leukemia, Hodgkins disease and non-Hodgkins’s lymphoma

Along with LD-3, ____________ and _________ are also increased in carcinomas.

LD-1 and LD-5

______________ is the most elevated in cancer of testis and ovary.

LD-1

The ______________ and _________________ are found primarily in liver and skeletal muscle tissue.

LD-4 and LD-5 isoenzyme

_______________ is the predominant fraction in these tissues.

LD-5

LD-5 levels have greatest clinical significance in the detection of _______________, particularly ________________ and _________________________.

hepatic disorders

intrahepatic disorders and muscle dystrophies

Elevations are especially high (10 times the normal) in ____________________ with lower values in observed in _____________.

toxic hepatitis with jaundice

viral hepatitis

Elevated LD in CSF is also observed in cases of _______________, _______________, _______________ of the brain.

bacterial meningitis, cerebral hemorrhage and neoplasms

In urine, elevation is also seen in ________________, _________________, __________________.

neoplasm of the prostate, kidneys and urinary bladder.