• Purity

  >95%, by SDS-PAGE with silver staining

• Endotoxin Level

  <0.10 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its ability to enhance survival of ATDC5 mouse chondrogenic cells. The ED    ₅₀ for this effect is 0.8-4 μg/mL. Measured by its ability to phosphorylate D-xylose. The specific activity is >15 pmol/min/μg, as measured under the described conditions. See Activity Assay Protocol on .

• Source

  Chinese Hamster Ovary cell line, CHO-derived Asn27-Leu409, with an N-terminal HA tag

• Accession #

• N-terminal Sequence    
  Analysis

  Tyr

• Predicted Molecular Mass

  44 kDa

• SDS-PAGE

  44-53 kDa, reducing conditions

Background: FAM20B

FAM20B is a member of the FAM20 protein family that has three members in mammals (FAM20A, FAM20B, FAM20C) (1). Human FAM20B shares 97% amino acid sequence identity with mouse and rat FAM20B. FAM20B localizes to the Golgi apparatus where it phosphorylates the xylose residue in the glycosaminoglycan (GAG)-protein linkage region of proteoglycans, which leads to enhanced GAG biosynthesis (2). Accordingly, chondroitin sulfate and heparan sulfate production is increased when FAM20B is over-expressed and reduced following FAM20B knockdown (2). FAM20B knockout mice display embryonic lethality at day E13.5, suggesting that FAM20B has an important role during development (3). Furthermore, in zebrafish, FAM20B mutations result in reduced cartilage matrix production and skeletal defects (4). The enzymatic activity of recombinant human FAM20B is measured using a phosphatase-coupled method (5).

• References:

1. Nalbant, D. et al. (2005) BMC Genomics 6:11.

2. Koike, T. et al. (2009) Biochem. J. 421:157.

3. Vogel, P. et al. (2012) Vet. Pathol. 49:998.

4. Eames, B.F. et al. (2011) PLoS Genet. 7:e1002246.

5. Wu, Z.L. (2011) PLoS One 6:e23172.

• Long Name:

  Family with Sequence Similarity 20, Member B

• Entrez Gene IDs:

  9917 (Human); 215015 (Mouse); 304885 (Rat)

• Alternate Names:

  EC 2.7.1.-; FAM20B; family with sequence similarity 20, member B; Glycosaminoglycan Xylosylkinase; gxk1; KIAA0475; Protein FAM20B; XYLK; Xylose Kinase