ALS (Acid Labile Subunit) ELISA Assay Kit

$540.00

The Eagle Biosciences ALS ELISA Assay kit is suited for measuring ALS in human serum or EDTA-/heparin-/citrate plasma. The Eagle Biosciences Human ALS ELISA Assay kit is for Research Use Only.

ALS (Acid Labile Subunit) ELISA Assay Kit

For Research Use Only

Size: 1×96 wells
Sensitivity: 0.53 ng/mL
Assay Range: 0.53 – 30,000 ng/mL
Incubation Time: 3 hours
Sample Type: Serum, Plasma
Sample Size: 10 ul

ALS (Acid Labile Subunit) ELISA is manufactured by Mediagnost

Additional Information

Assay Background


The Insulin-like Growth Factors (IGF) – I and II are bound to specific binding proteins in circulation (IGFBP). Until today seven different proteins have been identified IGFBP-1 to 7 [1, 2]. IGF bioavailablity, transport and storage is regulated or facilitated by these binding proteins which are expressed differentially according physiological and developmental requirements. The most abundant IGFBP in circulation is IGFBP-3. Together with IGFBP-5 it is able to form the so called ternary complex with IGF and the acid-labile subunit (ALS) [3-5]. In the circulation nearly all IGF is bound in this ternary complex and thus not able to cross the endothelial barrier. Only very small amounts of IGF or IGFBP-3 exist outside this complex [6, 7]. The acid-labile subunit is an important part of the IGF-storage mechanism in circulation. In ALS deficiency or in ALS knock-out mice the concentration of IGF and IGFBP-3 in the circulation is significantly decreased resulting in impaired growth [10].

The acid-labile Subunit, is a synthezised as propeptide of 605 amino acids. The signal peptide, necessary for ALS secretion (AA 1-27) cleaved off enduring the transport process (Swiss-Prot P35858 Version 82). The mature protein consists of 578 amino acids and contains about 20 leucin rich sequence repeats. Beside the leucin-rich repeats several potential N-linked glycosylation sides have been described. Miller BS et al. were able to demonstrate that incomplete glycolsylation of IGFs, ALS and IGFBP-3 results in a decreased serum concentration of these proteins. Oral mannose therapy resulted in a partial normalization of the glycosylation pattern and went along with improved growth [8]. Mutations in or the complete knock out of the ALS gene result in IGF / IGFBP-3 deficiency and therewith in disturbation of growth [9,10]. Beside growth also other endocrine axes may be involved. In primary ALS deficiency hyperinsulinemia could be observed [11, 12]. Further, the ALS-IGF-IGFBP-system seems to be of relevance in coronary disease [13].

The first ALS immunoassay was described by Baxter RC in 1990 [6]. By this in-house radioimmunoassay it was shown that ALS is present in high concentrations in serum (50µg/mL) of healthy humans. But not detectable in other body fluids like amniotic fluid, cerebrospinal fluid or seminal plasma – in spite of the fact that these body fluids contain high level IGFBP-3.

Assay Principle


The Eagle Biosciences ALS ELISA is a so-called Sandwich-Assay. It utilizes two specific and high affinity antibodies for this protein. These antibodies were created by immunization of rabbits with specific peptides as previously described by Khosravi and Stadler [16, 17].

The ALS in the sample binds to the immobilized first antibody on the microtiter plate. The biotinylated second anti-ALS-Antibody binds also to the immobilized ALS. In the following step the Streptavidin-POD-Conjugate binds to the biotinylated antibody and in the closing substrate reaction the turn of the colour will be catalysed, quantitatively depending on the ALS-level of the samples.
Initially the test system was calibrated against an internal serum standard and measurement results were expressed as Mediagnost mU/mL. After successful production of eukaryotic recombinant ALS the calibration was transferred to mass units (see Calibration / Traceability).

Additionally recombinant material was used to quantify the ALS content of the calibrators in mass units. Thorough analysis revealed that 1 mU ALS is equivalent to 5 ng ALS and all previous assay data describing the assay performance were accordingly transferred to ng/mL.

Linearity


Measured signal intensity [OD450] of differentially diluted samples. The recommended dilution is 1:150 (0.007).

Manual

Product Manual