Test ID: TPPTF
Tripeptidyl Peptidase 1 (TPP1) and Palmitoyl-Protein Thioesterase 1 (PPT1), Fibroblasts
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluation of patients with clinical presentations suggestive of neuronal ceroid lipofuscinoses (NCL)
An aid in the differential diagnosis of infantile and late infantile NCL
Additional Tests Lists test(s) that are always performed, at an additional charge, with the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| FIBR | Fibroblast Culture | Yes | Yes |
| CRYOB | Cryopreserve for Biochem Studies | No | Yes |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
When this test is ordered, a fibroblast culture and cryopreservation for biochemical studies will always be performed at an additional charge. However, for multiple lysosomal enzyme assays on a patient utilizing fibroblast culture, only 1 culture is required regardless of the number of enzyme assays ordered. If viable cells are not obtained within 10 days, client will be notified.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
TPPTF/89540: Fluorometric Enzyme Assay
FIBR/8482: Cultivated from Biopsy as Monolayer
CRYOB/88832: Fibroblast Subculture Followed by Cryopreservation and Storage
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
CLN2
INCL
LINCL
NCL1
NCL2
Palmitoyl-Protein Thioesterase 1 (PPT1)
TPP1 (Tripeptidyl Peptidase 1)
NCL (Neuronal Ceroid Lipofuscinosis)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
This test is not recommended for prenatal testing.
Forms:
1. 1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. 2. If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
Submit only 1 of the following specimens:
Specimen Type: Cultured fibroblasts
Container/Tube: T-75 or T-25 flask
Specimen Volume: 1 full T-75 flask or 2 full T-25 flasks
Specimen Stability Information: Ambient (preferred)/Refrigerated <24 hours
Specimen Type: Skin biopsy
Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [Supply T115]).
Specimen Volume: 4-mm punch
Specimen Stability Information: Refrigerated (preferred)/Ambient
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Specimen in formalin or fixative preservative |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Tissue | Varies | |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The neuronal ceroid lipofuscinoses (NCL) comprise a group of recessively inherited neurodegenerative disorders involved in lysosomal protein catabolism. Clinically, they are characterized by vision loss, seizures, mental regression, behavioral changes, movement disorders, and the accumulation of storage material with a characteristic appearance by electron microscopy. Currently, at least 10 genetically distinct NCLs (CLN1-CLN10) are known. The age of onset and rate of deterioration varies according to type of NCL. Tissue damage is selective for the nervous system and many patients die in the first decade of life due to central nervous system degeneration. There is an overall incidence in the United States estimated at 1 in 12,500.
Children affected by infantile NCL (CLN1) typically have normal growth and development until about 6 to 12 months of age. Slowed head growth occurs at around 9 months followed by psychomotor degeneration, seizures, and progressive macular degeneration leading to blindness by the age of 2. CLN1 is caused by a deficiency of the lysosomal enzyme palmitoyl-protein thioesterase 1 (PPT1), which cleaves long-chain fatty acids (usually palmitate) from cysteine residues. Electron microscopy shows granular osmophilic deposits (GRODs) in most cell types. PPT1 is thought to play an active role in various cell processes including apoptosis, endocytosis, and lipid metabolism. Infantile NCL has an incidence of 1 in 20,000 in Finland and is rare elsewhere.
The late infantile form of NCL (CLN2) is caused by deficiency of the lysosomal enzyme tripeptidyl peptidase 1 (TPP1), which cleaves tripeptides from the N-terminus of polypeptides. Tissue damage results from the defective degradation and consequent accumulation of storage material with a curvilinear profile by electron microscopy. There is widespread loss of neuronal tissue especially in the cerebellum and hippocampal region. Disease onset occurs at 2 to 4 years of age with seizures, ataxia, myoclonus, psychomotor retardation, vision loss and speech impairment.
Diagnostic strategy depends on the age of onset of symptoms. In children presenting between the ages 0 to 4 years, enzyme assay of PPT1 and TPP1 is an appropriate first step. In addition, molecular genetic testing of CLN1 or CLN2 may allow for identification of the disease causing mutations.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
TPP1: 69-934 nmol/h/mg Prot
PPT1: 30-194 nmol/h/mg Prot
Interpretation Provides information to assist in interpretation of the test results
Tripeptidyl peptidase 1 (TPP1) and palmitoyl-protein thioesterase 1 (PPT1) enzyme activity below 5 nmol/h/mg of protein are highly suggestive of late infantile and infantile neuronal ceroid lipofuscinoses, respectively.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This assay does not detect carrier status of neuronal ceroid lipofuscinoses.
Some variants with age of onset occurring in older individuals have been noted.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Haltia M: The neuronal ceroid-lipofuscinoses: from past to present. Biochem Biophys Acta 2006;1762:850-856
2. Kavianen R: Juvenile-onset neuronal ceroid liposuscinosis with infantile CLN1 mutation and palmitoyl-protein thioesterase deficiency. Eur J Neur 2007;14:369-372
3. Enns GM, Steiner RD, Cowan TM: Lysosomal disorders. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 749-750
Method Description Describes how the test is performed and provides a method-specific reference
The synthetic substrate for palmitoyl-protein thioesterase 1 (PPT1) is 4-methylumbelliferyl-6-thioplamitoyl-beta-glucoside. The fibroblasts are homogenized. Approximately 10 mcg of protein is combined with substrate and incubated at 37 degrees C for 1 hour. The reaction is stopped with a glycine buffer. The fluorescence of the 4-methylumbelliferone product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1 hour incubation period.(Van Diggelen OP, Keulemans JLM, Winchester B, et al: A rapid fluorogenic palmitoyl-protein thioesterase assay: Pre and post natal diagnosis of INCL. Mol Genet Metab 1999;66:240-244)
The synthetic substrate tripeptidyl peptidase 1 (TPP1) is Ala-Ala-Phe-7-amino-4-methylcoumarin. The fibroblasts are homogenized. Approximately 5 mcg of protein is combined with substrate and incubated at 37 degrees C for 1 hour. The reaction is stopped with a glycine buffer. The fluorescence of the 7-amino-4-methylcoumarin product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1 hour incubation period.(Sohar I, Lin L, Lobel P: Enzyme-based diagnosis of classical late infantile neuronal ceroid lipofuscinosis: comparison of tripeptidyl peptidase I and pepstatin-insensitive protease assays. Clin Chem 2000;46:1005-1008)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Thursday
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
82657-TPP1 and PPT1
88233-Fibroblast culture
88240-Cryopreservation for biochemical studies
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 50791 | Specimen | 31208-2 |
| 50792 | Specimen ID | N/A |
| 50793 | Source | N/A |
| 50794 | Order Date | N/A |
| 50795 | Reason For Referral | 42349-1 |
| 50796 | Method | In Process |
| 50797 | TPP1, F | In Process |
| 50798 | PPT1, F | 34647-8 |
| 50799 | Interpretation | 59462-2 |
| 50800 | Amendment | In Process |
| 50801 | Reviewed By | N/A |
| 50802 | Release Date | N/A |
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