DESCRIPTION

CPD is a membrane-bound glycoprotein with three carboxypeptidase-like domains, but only the first two domains have enzymatic activity. It plays a key role in the processing and modification of protein, ensuring the correct folding and function of the newly synthesized protein. CPD is a membrane-bound component of Golgi negative network, which circulates to the cell surface through secretion and endocytosis. The results show that the two active domains of CPD have different preferences for substrates. The first domain prefers C-terminal arginine, while the second domain has the same number of substrates for lysine and arginine. Although the specific role of CPD in some diseases has not been fully understood, studies have shown that its abnormal expression may be related to the development of cancer, especially in tumor cells.

PRINCIPLE OF THE ASSAY

Sandwich ELISA structure (Detection antibody labeled with HRP) A capture antibody is pre-coated onto the bottom of wells which binds to analyte of interest. A detection antibody labeled with HRP also binds to the analyte. TMB acts as the HRP substrate and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns solution yellow. The color intensity is proportional to the quantity of bound protein which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	8	11.66	0.41	3.51
2	8	3.17	0.08	2.57
3	8	0.99	0.07	7.10

Inter-assay Precision

Sample	n	Mean (ng/mL)	SD	CV%
1	16	11.94	0.49	4.13
2	16	3.16	0.10	3.07
3	16	0.95	0.07	6.86

RECOVERY

The recovery of human CPD spiked to three different levels throughout the range of the assay in cell lysate was evaluated.

Sample Type		Average% of Expected	Range (%)
Cell lysate	1:16	83	80-88
	1:32	83	80-85

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The cell lysate was initially diluted 1:2.)

		Cell lysate
1:2	Average% of Expected	100
	Range (%)	-
1:4	Average% of Expected	92
	Range (%)	90-94
1:8	Average% of Expected	84
	Range (%)	80-88
1:16	Average% of Expected	96
	Range (%)	81-111

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human CPD Sandwich ELISA Kit produced at Sunlong Medical™.